Prasanna, Author at BTech Geeks

Servlet example eclipse – How to Create Hello World Servlet Example using Eclipse IDE with Tomcat 7? | Servlet Hello World Example in Eclipse IDE with Tomcat

September 7, 2022 by Prasanna

Servlet example eclipse: This tutorial will give you insight into how to run a servlet class that prints the “Hello World” String in the Browser. Here we are going to use the Eclipse IDE to develop code and will run the code in Tomcat Webserver. Creating Servlet in IDE Environment will save you from doing a lot of work. We have outlined the steps to be done in order to create a Hello World Servlet Example using Eclipse IDE in detail.

Tomcat Servlet using Eclipse IDE

Tomcat Servlet using Eclipse IDE

For creating a Hello World Servlet Example using eclipse IDE with tomcat 7, you just need two things:

i) Download and install Eclipse IDE for Java EE developers.

Download Eclipse IDE: eclipse ide for java ee developer

ii) Download and install the Apache Tomcat server

Download Tomcat Server:
After download and install Eclipse IDE for Java EE developer and Tomcat Server, you will be able to create a Hello World Servlet Example using Eclipse IDE.

Do Refer:

1. Create a Dynamic Web Project

To create a Dynamic web project open eclipse ide → Go to menu → New → Dynamic web project.

Write your project name and click on next.

Click on the next button

check on generate web.xml and click on the finish button.

Once you click on the finish button, your Eclipse IDE will automatically create a dynamic web project as follows

2. Create a Servlet Class

After creating a dynamic web project the next step is to create a servlet class. right-click on your project → New → Servlet

Write the package name in the java package field and class name in the class name field and then click on next.

You can mention the URL mapping in the following screen(web.xml) and click on next.

Click on the finish button.

On Clicking the finish button, your Eclipse IDE will generate a servlet class depending on the configuration provided in earlier steps as under.

3. Write your Custom Code

Write down your code in doGet() method and call to setContentType() establishes the MIME types of the HTTP response. In this program,the MIME type is text/html.Next the getWriter() method obtains a PrintWriter. Later use println() to write some HTML code as HTTP response.

4. Run your Servlet Code

In Order to run your Servlet code right-click on your project → Run As → 1 Run on Server.

Choose the existing Tomcat Server and then Click on the finish button.

5. The Output on Browser

Your Eclipse IDE will generate output on your own browser and print “HELLO WORLD” on the browser.

Time complexity interview questions – Python Interview Questions on Algorithm Analysis and Big-O

September 7, 2022September 7, 2022 by Prasanna

Time complexity interview questions: We have compiled most frequently asked Python Interview Questions which will help you with different expertise levels.

Python Interview Questions on Algorithm Analysis and Big-O

Algorithm

Big o python: An algorithm is a procedure or set of instructions that are carried out in order to solve a problem. Coding demands procedural knowledge which is expressed in the form of algorithms. An algorithm provides a recipe or a roadmap or a simple sequence of instructions that are required to accomplish a particular programming task. So, for things as simple as adding two numbers or as complex as designing a banking program, everything requires a systematic approach. It is important to create a roadmap that makes sense before going ahead with the coding part. For simple programs, it is easy to create algorithms through logical thinking. There are also some famous algorithms that can be used for complex problem solving and hence are frequently used for coding.

Question 1.
What are the steps involved in writing an algorithm?
Answer:
There are three main steps involved in writing an algorithm:

1. Data Input

Formulate the problem and decide what data types will be the input.

2. Data Processing

Decide what computation will be carried off to get the desired result.
Also identify the decision points, conditions under which various functions will operate.

3. Results Output

One should know the expected results so that they can be verified by the actual results.

Question 2.
What are the characteristics of the Algorithm?
Answer:
An algorithm has the following five characteristics:

Precision: It clearly defines one single starting point and one or more well-defined ending points.
Effectiveness: It is composed of effective primitives that are understood by the person or machine using it.
Input/Output Specified: The algorithm must receive input and it must also produce an output.
Finiteness: An algorithm stops after the execution of a finite number of steps.
Uniqueness: In an algorithm, the result of every step is uniquely defined and its value depends only on the input provided and the output generated by the previous steps.

Question 3.
What is the meaning of Problem solving?
Answer:
Problem-solving is a logical process in which a problem is first broken down into smaller parts that can be solved step by step to get the desired solution.

Question 4.
What would you call an algorithm that puts element lists in a certain order?
Answer:
An algorithm that puts elements of a list in a certain order is called a sorting algorithm. It uncovers a structure by sorting the input. Sorting is often required for optimizing the efficiency of other algorithms. The output of a sorting algorithm is in non-decreasing order where no element is smaller than the original element of the input and the output reorders but retains all the elements of the input which is generally in array form.
Some very commonly known sorting algorithms are as follows:

1. Simple sorts:
a. Insertion sort
b. Selection sort

2. Efficient Sorts:
a. Merge sort
b. Heap sort
c. Quick sort
d. Shell sort

3. Bubble sort

4. Distribution sort
a. Counting sort
b. Bucket sort
c. Radix sort

Question 5.
What type of algorithm calls itself with smaller or simpler input values?
Answer:
A recursive algorithm calls itself with smaller input values. It is used if a problem can be solved by using its own smaller versions.

Question 6.
What is the purpose of the divide and conquer algorithm? Where is it used?
Answer:
As the name suggests the divide and conquers algorithm divides the problem into smaller parts. These smaller parts are solved and the solutions obtained are used to solve the original problem. It is used in Binary search, Merge sort, quick sort to name a few.

Question 7.
What is dynamic programming?
Answer:
In a dynamic problem, an optimization problem is broken down into much simpler sub-problems, each sub-problem is solved only once and the result is stored. For example, Fibonacci Sequence (Explained in Chapter on Recursion).

Big-O Notation

Big-0 notation helps you analyze how an algorithm would perform if the data involved in the process increases or in simple words it is a simplified analysis of how efficient an algorithm can be.

Since algorithms are an essential part of software programming it is important for us to have some idea about how long an algorithm would take to run, only then can we compare two algorithms and a good developer would always consider time complexity while planning the coding process.

It helps in identifying how long an algorithm takes to run.

Big-O

(1) Gives us the algorithm complexity in terms of input size n.
(2) It considers only the steps involved in the algorithm.
(3) Big-O analysis can be used to analyze both time and space.

An algorithm’s efficiency can be measured in terms of the best-average or worst case but Big-O notation goes with the worst case scenario.
It is possible to perform a task in different ways which means that there can be different algorithms for the same task having different complexity and scalability.
Now, suppose there are two functions:

Constant Complexity [0(1)]

A task that is constant will never experience variation during runtime, irrespective of the input value. For Example:
>>> x = 5 + 7
>>> x
12
>>>
The statement x = 5+7 does not depend on the input size of data in any way. This is known as 0(l)(big oh of 1).
Example:
Suppose, there are sequence of steps all of constant time as shown in the following code:
>>> a= (4-6) + 9
>>> b = (5 * 8) +8
>>> print (a * b)
336
>>>
Now let’s compute the Big-0 for these steps:
Total time = O(1)+O(1)+O(1)
= 3O(1)
While computing Big – O we ignore constants because once the data size increases, the value of constant does not matter.
Hence the Big-0 would be 0(1).

Linear complexity: [O(n)]

In the case of linear complexity, the time taken depends on the value of the input provided.
Suppose you want to print a table of 5. Have a look at the following code:
>>> for i in range(0,n):
print (“\n 5 x “,i,”=”,5*i)
The number of lines to be printed depends on ‘n’. For n =10, only ten lines will be printed but for n= 1000, the for loop will take more time to execute.
The print statement is O(1).
So, the block of code is n*O(l) which is 0(n).
Consider following lines of code:
>>>j = 0 ————(1)
>>> for i in range(0,n) : ————(2)
print(“\n 5 x “,i,”=”,5*i)
(1) is O(1)
(2) block is O(n)
Total time = O(l)+O(n)

We can drop O(1) because it is a lower order term and as the value of n becomes large (1) will not matter and the runtime actually depends on the for a loop.
Hence the Big-0 for the code mentioned above is O(n).

Quadratic Complexity: [O(n²)]

As the name indicates quadratic complexity, the time taken depends on the square of the input value. This can be the case with nested loops. Look at the following code:

>>> for i in range (0,n):
for j in range(0,n):
print(“I am in “, j,” loop of i = “, i,”.”)

In this piece of code, the print statement is executed n2 times.

Logarithmic Complexity

Logarithmic complexity indicates that in the worst case the algorithm will have to perform log(n) steps. To understand this, let’s first understand the concept of the logarithm.

Logarithms are nothing but the inverse of exponentiation.

Now let’s take term 2³. Here 2 is the base and 3 is the exponent. We, therefore, say that base 2 logs of 8 (log₂ 8) = 3. Same way if then base 10⁵ = 100000 then base 10 log of 100000 (log₁₀ of 100000) = 5.

Since the computer works with binary numbers, therefore in programming and Big O we generally work with base 2 logs.

Have a look at the following observation:

1. 2⁰ = 1, log₂ 1 = 0
2. 2¹ = 2, log₂ 2 = 1,
3. 2² = 4, log₂ 4 = 2,
4. 2³ = 8, log₂ 8 = 3,
5. 2⁴= 16,log₂ 16 = 4,
This means that if n =1, the number of steps = 1.
If n = 4, the number of steps will be 2.
If n = 8, then the number of steps will be 3.
So, as data doubles the number of steps increases by one.
The number of steps grows slowly in comparison to the growth in data size.
The best example of logarithmic complexity in software programming is the Binary Search tree. You will learn more about it in the chapter based on Trees.

Question 8.
What is worst-case time complexity of an algorithm?
Answer.
The worst-case time complexity in computer science means worst-case in terms of time consumed while execution of a program. It is the longest-running time that an algorithm can take. The efficiency of algorithms can be compared by looking at the order of growth of the worst-case complexity.

Question 9.
What is the importance of Big-O notation?
Answer:
Big-0 notation describes how fast the runtime of an algorithm will increase with respect to the size of the input. It would give you a fair idea about how your algorithm would scale and also give you an idea about the worst-case complexity of the algorithms that you might be considering for your project. You would be able to compare two algorithms and decide which would be a better option for you.

Question 10.
What is the need for run-time analysis for an algorithm when you can find the exact runtime for a piece of code?
Answer:
The exact runtime is not. considered because the results can vary depending on the hardware of the machine, the speed of the processor, and the other processors that are running in the background. What is more important to understand is that how the performance of the algorithm gets affected with an increase in input data.

Question 11.
The big-O analysis is also known as.
Answer:
Asymptotic analysis

Question 12.
What do you understand by asymptotic notation?
Answer:
It is very important to know how fast a program would run and as mentioned earlier we do not want to consider the exact ran time because different computers have different hardware capabilities and we may not get the correct information in this manner.
In order to resolve this issue, the concept of asymptotic notation was developed. It provides a universal approach for measuring the speed and efficiency of an algorithm. For applications dealing with large inputs we are more interested in behaviour of an algorithm as the input size increases. Big O notation is one of the most important asymptotic notations.

Question 13.
Why is Big O notation expressed as O(n)?
Answer:
Big-0 notation compares the runtime for various types of input sizes. The focus is only on the impact of input size on the runtime which is why we use the n notation. As the value of n increases, our only concern is to see how it affects the runtime. If we had been measuring the runtime directly then the unit of measurement would have been time units like second, micro-second, and so on. However, in this case, ‘n’ represents the size of the input, and ‘O’ stands for ‘Order’. Hence, 0(1) stands for the order of 1, 0(n) stands for the order of n, and 0(n²) stands for the order of the square of the size of the input.
Big-0 notations and names:

Constant – 0(1)
Logarithmic – 0(log(n))
Linear -0(n)
Log Linear – 0(nlog(n))
Quadratic – 0(«2)
Cubic – 0(«3)
Exponential – 0(2″)

Question 14.
Write a code in python that takes a list of alphabets such as [‘a’ , ‘b’ , ‘c’, ‘d’ , ‘e’ , ’f’ , ’g’] and returns a list of combination such as [‘bcdefg’, ‘acdefg’, ‘abdefg’, ‘abcefg’, ‘abcdfg’, ‘abcdeg’, ‘abcdef’]. Find the time complexity for the code.
Answer:
Code

input_value = input("enter the list of alphabets separate by comma : ")
alphabets = input_value.split(' , ')
final = [ ]
str = ' '
for element in range(0,len(alphabets)):
for index, item in alphabets:
if(item != alphabets[element]):
str = str+item
final. append (str)
str=' '

Execution

print (final)

Output

enter the list of alphabets seperate by comma : a,b,c,d,e,f,g
[‘bcdefg’, ‘acdefg’, ‘abdefg’, ‘abcefg’, ‘abcdfg’, ‘abcdeg’, ‘abcdef’]
>>>

Conclusion:

The code has a runtime of O(n<sup>2</sup>).

Question 15.
The following code finds the sum of all elements in a list. What is its time complexity?

def sum(input_list):
total = 0
for i in input_list:
total = total + i
print(total)

Answer:

def sum(input_list):
total = 0                              -----------(1)
for i in input list:                   -----------(2)
total = total + i
         print(total)                  -----------  (3)
time for block (1) = O(1)
time for block (2) = O(n)
time for block (3) = O(1)
Total time = O(1) + O(n) + O(1)
Dropping constants
Total time = O(n)

Question 16.
What are the pros and cons of time complexity?
Answer:
Pros:
It is a good way of getting an idea about the efficiency of the algorithm.
Cons:
It can be difficult to assess complexity for complicated functions.

Question 17.
What is the difference between time and space complexity?
Answer:
Time complexity gives an idea about the number of steps that would be involved in order to solve a problem. The general order of complexity in ascending order is as follows:

O(1) < O(log n) < O(n) < O(n log n) <O(n<sup>2</sup>)

Unlike time, memory can be reused and people are more interested in how fast the calculations can be done. This is one main reason why time complexity is often discussed more than space complexity. However, space complexity is never ignored. Space complexity decides how much memory will be required to run a program completely. Memory is required for:

Instruction space
Knowledge space for constants, variables, structured variables, dynamically altered areas, etc
Execution

Question 18.
What is the difference between auxiliary space and space complexity?
Answer:
Auxiliary space is the extra space that is required while executing an algorithm and it is temporary space.
Space complexity on the other hand is the sum of auxiliary space and input space:

Space complexity = Auxiliary space + Input space

Question 19.
What is the memory usage while executing the algorithm?
Answer:
Memory is used for:

Saving the compiled version of instructions.
In the case of nested functions or one algorithm, calling another algorithm, the variables are pushed to a system stack and made to wait till the internal algorithm has finished executing.
To store data and variables.

Space Complexity

You have learned about time complexity. Now, let’s move on to space complexity. As the name suggests space complexity describes how much memory space would be required if the size of input n increases. Here too we consider the worst-case scenario.

Now have a look at the following code:
>>> X = 23 (1)
>>> y = 34 (2)
>>> sum = x + y (3)
>>> sum
57
>>>

In this example, we need space to store three variables: x in (1), y in (2), and sum in (3). However, this scenario will not change, and the requirement for 3 variables is constant and hence the space complexity is 0(1).

Now, have a look at the following code:

word = input(“enter a word : “)
word_list = [ ]
for element in word:
print(element)
word_list.append(element)
print(word_list)

The size of the word_list object increase with n. Hence, in this case, the space complexity is 0(n).

If there is a function 1 which has to suppose three variables and this functional calls another function named function2 that has 6 variables then the overall requirement for temporary workspace is 9 units. Even if functional calls function2 ten times the workspace requirement will remain the same.

Question 20.
What would be the space complexity for the following piece of code? Explain.

n = int(input("provide a number : "))
statement = "Happy birthday"
for i in range(0,n):
print(i+1,". ”, statement)

Answer:
The space complexity for the above code will be 0(1) because the space requirement is only for storing value of integer variable n and string statement. Even if the size of n increases the space requirement remains constant. Hence, 0(1).

Question 21.
What is the time and space complexity for the following:

a = b = 0
for i in range(n):
a = a + i
for j in range(m):
b = b + j

Answer:
Timecomplexity
Time for first loop = O(n)
Time for second loop = O(m)
Total time = O(n) + O(m) = O(n + m)
Space complexity
O(1)

Question 22.
Find the time complexity for the following code:

a = 0
for i in range(n):
a = a + i
for j in range(m):
a = a + i + j

Answer:
Time complexity: O(n²)

Question 23.
What will be the time complexity for the following code?

i = j = k =0
for i in range(n/2,n):
for j in range(2,n):
k = k+n/2
j = j*2

Answer:
The time complexity for the first for loop O(n/2).
The time complexity for second for loop: O(logn) because j is doubling itself till it is less than n.
Total time = O(n/2)*O(logn)
= O(nlogn)

Question 24.
What is the time complexity for the following code:

i = a = 0
while i>0:
a = a+i
i = i/2

Answer:
Time complexity will be O(logn).

Big O for Python Data Structures

Python language comprises mutable and immutable objects. Numbers, strings, and tuple come in the latter category whereas lists, sets, and dictionary data types are mutable objects. The reason why lists and dictionaries are called mutable is that they can be easily altered at any time. They are like arrays because the data elements can be inserted or deleted easily by providing an index value and since the values can be easily added or removed from any point, the lists are considered to be dynamic. Hence, lists are known to be dynamic arrays. You can also say that lists are called dynamic array because:

Its size can be dynamically modified at run time.
You need not define the size of the list when you create it.
They allow you to store more than one variable.
Dynamic arrays once filled allocate a bigger chunk of memory, and elements of the original array are copied to this section of the memory as a result it can continue to fill available slots.

The most important operations that are performed on a list are as follows:

Indexing
Assigning value to an index value

Both the methods mentioned above are designed to run at constant time 0(1). The Big-0 for common list operations are given as follows:

index[ ] : O(1)
index assignment: O(1)
append: O(1)
1. pop( ): O(1)
pop(i): O(n)
insert(i, item): O(n)
delete operator: O(n)
contains(in): O(n)
get slice[x:y]: O(k)
del slice: O(n)
set slice : O(n+k)
reverse: O(n)
concatenate: O(k)
sort: O(nlog n)
multiply O(nk)

Dictionaries

Dictionaries are implementation of hashtables and can be operated with keys and values.

Big-O efficiencies for common dictionary objects are given as follows:

copy : 0(n)
get item : 0(1)
set item: 0(1)
delete item : 0(1)
contains(in): 0(1)
iteration: 0(n)

Java continue outer loop – Java Continue Statement with Example | Continue Statement in Java with Nested Loop, For Loop, While Loop, Do-while Loop Programs

September 6, 2022 by Prasanna

Java continue outer loop: A programming language uses control statements to control the flow of execution of a program. In Java programming, we can control the flow of execution of a program based on some conditions. Java control statements can be put into the following three categories: selection, iteration, and jump. In this tutorial, we will learn about the Java continue statement with example programs and workings. The jump statement can be used to transfer the control to other parts of the program. The java continues statement is one of the jump statements.

Java Continue Statement
Syntax of Java Continue
Flow Diagram of Continue Statement
Working of Java continue statement
Continue Statement Example
Java Continue Statement with Nested Loop
Example of Continue with Nested Loop
Java Continue Statement with Labeled for Loop
Example of Labeled Continue Statement
Java Continue Statement with Inner Loop
Example on Continue with Inner Loop
Java Continue Statement in while loop
Example on Java Continue statement inside While loop
Java Continue Statement in do-while loop
Continue Statement in Java Example in Do-While loop

Java Continue Statement

The Java Continue Statement skips the current iteration of a for loop, while loop, and do-while loop. We can use a continue statement with all types of loops such as: for loop, while loop, and do-while loop. In the while and do-while loops, a continue statement causes control to be transferred directly to the conditional expression that controls the loop. In for loop, the control goes first to the iteration portion of the for statement and then to the conditional expression.

Syntax of Java Continue

continue;

Do Check:

Flow Diagram of Continue Statement

Working of Java continue statement

Continue Statement Example

class ContinueStatement{
public static void main(String args[]){
for(int i = 1; i<=10; i++){
if(i%2 == 0)
continue;
//print odd values.
System.out.print(i+ " ");
}
}
}

Output:

1 3 5 7 9

Java Continue Statement with Nested Loop

In terms of java nested loops, the continue statement jumps the current iteration of the innermost loop.

Working of Java Continue Statement with Nested Loops:

Example of Continue with Nested Loop:

class Main {
public static void main(String[] args) {

int i = 1, j = 1;

// outer loop
while (i <= 3) {

System.out.println("Outer Loop: " + i);

// inner loop
while(j <= 3) {

if(j == 2) {
j++;
continue;
}

System.out.println("Inner Loop: " + j);
j++;
}
i++;
}
}
}

Output:

Outer Loop: 1
Inner Loop: 1
Inner Loop: 3
Outer Loop: 2
Outer Loop: 3

Java Continue Statement with Labeled for Loop

As with the break statement, the continue may also specify a label to describe which enclosing loop to continue. Here is an example that demonstrates the use of a continue statement with a label inside an inner for loop.

Example of Labeled Continue Statement:

class LabelContinue{
public static void main(String args[]){
aa:
for(int i = 1; i<=3; i++){
bb:
for(int j = 1; j<=3; j++){
if(i==2 && j==2){
continue aa;
}
System.out.println(i+ " " +j);
}
}
}
}

Output:

Java Continue Statement with Inner Loop

In case, we use the continue statement inside the inner loop, then it continues the inner loop only. Let’s see the example program and understand the concept carefully:

Example on Continue with Inner Loop:

//Java Program to illustrate the use of continue statement
//inside an inner loop
public class ContinueExample2 {
public static void main(String[] args) {
//outer loop
for(int i=1;i<=3;i++){
//inner loop
for(int j=1;j<=3;j++){
if(i==2&&j==2){
//using continue statement inside inner loop
continue;
}
System.out.println(i+" "+j);
}
}
}
}

Output:

Java Continue Statement in while loop

We use the while loop when the number of iteration is not fixed. So, check out the example on java continue with while loop and grasp thoroughly.

Example on Java Continue statement inside While loop:

// Java Program to illustrate the use of continue statement
// inside the While loop
public class GFG {

// Main driver method
public static void main(String args[])
{
// Initializing a variable say it count to a value
// greater than the value greater among the loop
// values
int count = 20;

// While loop for iteration
while (count >= 0) {
if (count == 7 || count == 15) {
count--;
// Decrementing variable initialized above

// Showing continue execution inside loop
// skipping when count==7 or count==15
continue;
}

// Printing values after continue statement
System.out.print(count + " ");

// Decrementing the count variable
count--;
}
}
}

Output:

20 19 18 17 16 14 13 12 11 10 9 8 6 5 4 3 2 1 0

Java Continue Statement in do-while loop

A do-while loop is as same as the while loop, but it holds one dissimilarity. In a while loop, the condition is estimated before the execution of the loop’s body however in a do-while loop, the condition is assessed after the execution of the loop’s body. Check the sample program from the below section:

Continue Statement in Java Example in Do-While loop

public class ContinueExample{
public static void main(String args[]){
int i=1;
do
{
if (i==5)
{
i++;
continue;
}
System.out.print(i+ " ");
i++;
}while(i<10);

}
}

Output:

1 2 3 4 6 7 8 9

ASP.NET interview question pdf – ASP.NET Interview Questions and Answers for Freshers

September 6, 2022 by Prasanna

ASP.NET interview question pdf: We have compiled most frequently asked .NET Interview Questions which will help you with different expertise levels.

C#.NET Interview Questions and Answers for Freshers Pdf Free Download

Question 1.
What is ASP.Net?
Answer:
It is a framework developed by Microsoft on which we can develop new generation websites using web forms(aspx), MVC, HTML, Javascript, CSS, etc. Its successor of Microsoft Active Server Pages(ASP). Currently, there is ASP.NET 4.0, which is used to develop websites. There are various page extensions provided by Microsoft that are being used for website development. Eg: aspx, asmx, ascx, ashx, cs, vb, HTML, XML etc.

Question 2.
What are the advantages of ASP.NET?
Answer:
ASP.Net is the next generation of ASP technology platform. It is superior to ASP in the following ways:

Highly Scalable
Compiled Code
User Authentication
Language Support
Third-party control
Configuration and Deployment are easy,
Object and Page caching
Strict coding requirements

Question 3.
What’s the use of Response.Output.Write( )?
Answer:
We can write formatted output using Response.Output.Write( ).

Question 4.
In which event of page cycle is the ViewState available?
Answer:
After the lnit( ) and before the Page_Load().

Question 5.
What is the difference between Server. Transfer and Response. Redirect?
Answer:
In Server. Transfer page processing transfers from one page to the other page without making a round-trip back to the client’s browser. This provides a faster response with a little less overhead on the server. The client url history list or current url Server does not update in the case of the Server. Transfer.

Response. Redirect is used to redirect the user’s browser to another page or site. It performs a trip back to the client where the client’s browser is redirected to the new page. The user’s browser history list is updated to reflect the new address.

Question 6.
From which base class all Web Forms are inherited?
Answer:
Page class.

Question 7.
What are the different validators in ASP.NET?
Answer:

Required Field Validator
Range Validator
Compare Validator
Custom Validator
Regular expression Validator
Summary Validator

Question 8.
Which validator control do you use if you need to make sure the values in two different controls matched?
Answer:
Compare Validator control.

Question 9.
What is the concept of Postback in ASP.NET?
Answer:
Postback is a request which is sent from a client to the server from the same page user is working with. There is an HTTP POST request mechanism in ASP.NET. It posts a complete page back to the server to refresh the whole page.

Question 10.
What is the use of “isPostBack” property?
Answer:
The “IsPostBack” property of the page object is used to check that the page is posted back or not.

Question 11.
How do you identify that the Page is PostBack?
Answer:
There is a property named “IsPostBack” property in Post object, which can be checked to know that the page is posted back.

Question 12.
What is ViewState?
Answer:
ViewState is used to retain the state of server-side objects between page post-backs.

Question 13.
Where the ViewState is stored after the page postback?
Answer:
ViewState is stored in a hidden field on the page on the client-side. ViewState is transported to the client and back to the server and is not stored on the server or any other external source.

Question 14.
How long the items in ViewState exists?
Answer:
They exist for the life of the current page.

Question 15.
What are the different Session state management options available in ASP.NET?
Answer:

In-Process
Out-of-Process.

In-Process stores the session in memory on the web server.
Out-of-Process Session state management stores data in an external server. The external server may be either a SQL Server or a State Server. All objects stored in session are required to be serializable for Out-of-Process state management.

Question 16.
How you can add an event handler?
Answer:
Using the Attributes property of server side control, e.g.
btnSubmit.Attributes.Add(“onMouseOver,,;,,JavascriptCode( );”)

Question 17.
What is caching?

Caching is a technique used to increase performance by keeping frequently accessed data or files in memory. The request for a cached file/data will be accessed from cache instead of actual location of that file.

Question 18.
what are the main requirements for caching?
Answer:

By caching the response, your request is served by the response already stored in memory.
You must be very careful while choosing the items to cache because Caching incurs overhead.
A frequently used web form which data doesn’t frequently change is good for caching.
A cached web form freezes form?s server-side content, and changes to that content do not appear until the cache is refreshed.

Question 19.
What are the different types of caching?ASP.NET has 3 kinds of caching :
Answer:

Output Caching,
Fragment Caching,
Data Caching.

Question 20.
Which type if caching will be used if we want to cache the portion of a page instead of whole page?
Answer:
Fragment Caching: It caches the portion of the page generated by the request. For that, we can create user controls with the below code:
<%@ OutputCache Duration=”120″ VaryByParam=”CategorylD;SelectedlD”%>

Question 21.
List the events in page life cycle.
Answer:

Page_Prelnit
Page_lnit
Page_lnitComplete
Page_PreLoad
Page_Load
Page_LoadComplete
Page_PreRender
Render

Question 22.
Can we have a web application running without web.Config file?
Answer:
Yes

Question 23.
What is the difference between ASP.NET Webforms and ASP.NET MVC?
Answer:
ASP.NET Webforms uses the page controller approach for rendering layout. In this approach, every page has its controller.
On the other hand, ASP.NET MVC uses the Front Controller approach. In this approach, there is a common controller for all pages.

Question 24.
Is it possible to create a web application with both webforms and MVC?
Answer:
Yes. We have to include the below MVC assembly references in the web forms application to create a hybrid application.

System.Web.Mvc 

System.Web.Razor


System. ComponentModel.DataAnnotations

Question 25.
Can we add code files of different languages in the App_Code folder?
Answer:
No. The code files must be in the same language to be kept in the App_code folder.

Question 26.
What is Protected Configuration?
Answer:
It is a feature used to secure connection string information.

Question 27.
Write code to send e-mail from an ASP.NET application?
Answer:

MailMessage mailMess = new MailMessage ( );
mailMess.From = "abc@gmail.com
             ";
mailMess.To = "xyz@gmail.com";
mailMess.Subject = "Test email";
mailMess.Body = "Hi This is a test mail.";
SmtpMail.SmtpServer = "localhost";
SmtpMail.Send (mailMess);

MailMessage and SmtpMail are classes defined System.Web.Mail namespace.

Question 28.
How can we prevent browser from caching an ASPX page?
Answer:
We can SetNoStore on HttpCachePolicy object exposed by the Response object’s Cache property:

Response.Cache.SetNoStore ( );
Response.Write (DateTime.Now.ToLongTimeString ());

Question 29.
What is the good practice to implement validations in aspx page?
Answer:
Client-side validation is the best way to validate data of a web page. It reduces the network traffic and saves server resources.

Question 30.
What is the use of Global.asax file?
Answer:
The Global.asax file is used to execute the application-level events and sets application- level variables.

Question 31.
What is event bubbling?
Answer:
When child control sends events to parent, it is termed as event bubbling. Server controls like Data Grid, Data List, and Repeater can have other child controls inside them.

Question 32.
What are the event handlers that we can have in Global.asax file?
Answer:
Application Events: Application_Start, Application_End, Application_AcquireRequestState, Application_AuthenticateRequest, Application_AuthorizeRequest, Application_BeginRequest, Application_Disposed, Application_EndRequest, Application_Error, Application_PostRequestHandlerExecute, Application_PreRequestHandlerExecute,Application_PreSendRequestContent, Application_PreSendRequestHeaders, Application_ReleaseRequestState, Application_ResolveRequestCache, Application_UpdateRequestCache

Session Events: Session_Start,Session_End

Question 33.
Which protocol is used to call a Web service?
Answer:
HTTP Protocol

Question 34.
Can we have multiple web config files for an asp.net application?
Answer:
Yes.

Question 35.
What is the difference between web config and machine config?
Answer:
Web config file is specific to a web application where as machine config is specific to a machine or server. There can be multiple web config files into an application where as we can have only one machine config file on a server.

Question 36.
Explain role based security ?
Answer:
Role-based security is used in almost all organization, and the Role-based security assigns certain privileges to each role.

Each user is assigned a particular role from the list.
Privileges as per role restrict the user’s actions on the system and ensure that a user can do only what he is permitted to do on the system.

<AUTHORIZATION>< authorization >
< allow roles="Domain_Name\Administrators" / > < !-- Allow Administrators in domain. 
 — >
< deny users-'*" />                             < !-- Deny anyone else. -- >
< /authorization >

Question 37.
What is Cross Page Posting?
Answer:
When we click submit button on a web page, the page post the data to the same page. The technique in which we post the data to different pages is called Cross Page posting. This can be achieved by setting POSTBACKURL property of the button that causes the postback. Findcontrol method of PreviousPage can be used to get the posted values on the page to which the page has been posted.

Question 38.
How can we apply Themes to an asp.net application?
Answer:
We can specify the theme in web.config file. Below is the code example to apply the theme:

<configuration> 

<system.web> 

<pages theme="Windows7" />

 </system.web> 

</configuration>

Question 39.
What is RedirectPermanent in ASP.Net?
Answer:
RedirectPermanent Performs a permanent redirection from the requested URL to the specified URL. Once the redirection is done, it also returns 301 Moved Permanently responses.

Question 40.
What is MVC?
Answer:
MVC is a framework used to create web applications. The web application base builds on Model-View-Controller pattern which separates the application logic from Ul, and the input and events from the user will be controlled by the Controller.

Question 41.
Explain the working of passport authentication.
Answer:
First of all it checks passport authentication cookie. If the cookie is not available then the application redirects the user to Passport Sign on page. Passport service authenticates the user details on sign on page and if valid then stores the authenticated cookie on client machine and then redirect the user to requested page

Question 42.
What are the advantages of Passport authentication?
Answer:
All the websites can be accessed using single login credentials. So no need to remember login credentials for each web site.

Users can maintain his/ her information in a single location.

Question 43.
What are the asp.net Security Controls?
Answer:

<asp:Login>: Provides a standard login capability that allows the users to enter their credentials
<asp:Loginl\lame>: Allows you to display the name of the logged-in user
<asp:LoginStatus>: Displays whether the user is authenticated or not
<asp:LoginView>: Provides various login views depending on the selected template
<asp:PasswordRecovery>: email the users their lost password

Question 44.
How do you register JavaScript for webcontrols ?
Answer:
We can register javascript for controls using <CONTROL -name>Attribtues.Add(scriptname,scripttext) method.

Question 45.
In which event are the controls fully loaded?
Answer:
Page load event.

Question 46.
what is boxing and unboxing?
Answer:
Boxing is assigning a value type to reference type variable. Unboxing is reverse of boxing ie. Assigning reference type variable to value type variable.

Question 47.
Differentiate strong typing and weak typing
Answer:
In strong typing, the data types of variable are checked at compile time. On the other hand, in case of weak typing the variable data types are checked at runtime. In case of strong typing, there is no chance of compilation error. Scripts use weak typing and hence issues arises at runtime.

Question 48.
How we can force all the validation controls to run?
Answer:
The Page.Validate( ) method is used to force all the validation controls to run and to perform validation.

Question 49.
List all templates of the Repeater control.
Answer:

ItemTemplate
AlternatingltemTemplate
SeparatorTemplate
HeaderTemplate
FooterTemplate

Question 50.
List the major built-in objects in ASP.NET?
Answer:

Application
Request
Response
Server
Session
Context

Question 51.
What is the appSettings Section in the web.config file?
Answer:
The appSettings block in the web config file sets the user-defined values for the whole application.
For example, in the following code snippet, the specified Connectionstring section is used throughout the project for database connection:

<emxconfiguration>
<appSettings>
<add key-'ConnectionString" value="server=local; pwd=password; database=default" /> 
</appSettings></em>

Question 52.
Which data type does the RangeValidator control support?
Answer:
The data types supported by the RangeValidator control are Integer, Double, String, Currency, and Date.

Question 53.
What is the difference between an HtmllnputCheckBox control and an HtmllnputRadioButton control?
Answer:
In HtmllnputCheckBoxcontrol, multiple item selection is possible whereas in HtmllnputRadioButton controls, we can select only single item from the group of items.

Question 54.
Which namespaces are necessary to create a localized application?
Answer:
System.Globalization
System.Resources

Question 55.
What is a cookie?
Answer:
A Cookie is a small piece of information which is stored at the client side. There are two types of cookie:

Session/Temporary Cookie: valid for a single session
Persistent Cookie: valid for multiple session

Question 56.
What is the default timeout for a cookie?
Answer:
30 minutes.

Question 57.
How would you turn off cookies on a page of a website?
Answer:
You have to follow the procedures given below:

Use the “Cookie.Discard” property,
It gets or sets the discard flag set by the server.
When set to true, this property instructs the client application not to save the Cookie on the hard disk of the user at the end of the session.

Question 58.
What are the different types of cookies in ASP.NET?
Answer:
Session Cookie – Resides on the client machine for a single session until the user does not log out.
Persistent Cookie – Resides on a user’s machine for a period specified for its expiry, such as 10 days, one month, and never.

Question 59.
What is the file extension of web service?
Answer:
Web services have file extension .asmx..

Question 60.
What are the components of ADO.NET?
Answer:
The components of ADO.Net are Dataset, Data Reader, Data Adaptor, Command, connection.

Question 61.
What is the difference between ExecuteScalar and ExecuteNonQuery?
Answer:
ExecuteScalar returns output value where as ExecuteNonQuery ctoes not return any value but the number of rows affected by the query. ExecuteScalar used for fetching a single value and ExecuteNonQuery used to execute Insert and Update statements.

Question 62.
What is IIS?
Answer:
IIS stands for Internet Information Services. It is created by Microsoft to provide Internet-based services to ASP.NET Web applications.

Question 63.
What is the usage of IIS?
Answer:
Following are the main usage of IIS:

IIS is used to make your computer to work as a Web server and provides the functionality to develop and deploy Web applications on the server,
IIS handles the request and response cycle on the Web server,
IIS also offers the services of SMTP and Frontpage server extensions.
The SMTP is used to send emails and use Frontpage server extensions to get the dynamic features of IIS, such as form handler.

Question 64.
What is a multilingual website?
Answer:
If a website provides content in many languages, it is known as a multilingual website. It contains multiple copies of its content and other resources, such as date and time, in different languages.

Question 65.
What is the parent class of all web server control?
Answer:
System. Web. Ul.Control class

Question 66.
What is the difference between the GET method () and POST method ()?
Answer:
GetMethod

Data is affixed to the URL.
Data is not secured.
Data transmission is faster in this method.
It is a single call system.
Only a limited amount of data can be sent.
It is a default method for many browsers.

PostMethod

Data is not affixed to the URL Data is secured.
Data transmission is comparatively slow
It is a two call system
A large amount of data can be sent
It is not set as default. It should be explicitly specified

Question 67.
What is the difference between session object and application object?
Answer:
The session object is used to maintain the session of each user. A session id is generated if a user enters in the application and when the user leaves the application, the session id is automatically deleted.
On the other hand, the application object is used to store the information and access variables from any page in the application.
Debug class is used to debug builds. Trace class is used for both debug and release builds.

Question 68.
What is the difference between trace and debug?
Answer:
Debug class is used to debug builds. Trace class is used for both debug and release builds.

Question 69.
What is the difference between client-side and server-side validations in WebPages?
Answer:
The client-side validation happens at the client’s side with the help of JavaScript and VBScript. This validation has occurred before the Web page is sent to the server. The server-side validation happens at the server side.

Question 70.
What is the difference between file-based dependency and key-based dependency?
Answer:
File-based dependency: File-based dependency facilitates you to save the dependency on a file in a disk.
Key-based dependency: In key-based dependency, you depend on another cached item.

Question 71.
What is the difference between globalization and localization?
Answer:
Globalization: Globalization is a technique to identify the part of a Web application that is different for different languages and separate it out from the web application.

Localization: In localization, you try to configure a Web application so that it can be supported for a specific language or locale.

Question 72.
What is the difference between a page theme and a global theme?
Answer:
Page Theme: The page theme is applied to particular web pages of the project. It is stored inside a subfolder of the App_Themes folder.
Global Theme: The Global theme is applied to all the web applications on the web server. It is stored inside the Themes folder on a Web server.

Question 73.
What is the difference between early binding and late binding?
Answer:
Early Binding: In early binding, a non-virtual method is called which is decided at a compile time.
Late Binding: In late binding, a virtual method is called which is decided at runtime.

Question 74.
What is the difference between server-side scripting and client-side scripting?
Answer:
Server-side scripting: In server-side scripting, all the script are executed by the server and interpreted as needed.

Client-side scripting: In client-side scripting, the script will be executed immediately in the browser such as form field validation, email validation, etc. The client-side scripting is usually carried out in VBScript or JavaScript.

Question 75.
How to sign out from forms authentication?
Answer:
FormsAuthentication.Signout() method is used to sign out from forms authentication.

Question 76.
How to display validation messages in one control?
Answer:
By the help of ValidationSummary control, we can display all validation messages in one control.

Question 77.
What is the difference between authentication and authorization?
Answer:
Authentication is a process of identifying user whereas authorization is used to check the access rights of an identified user.

Question 78.
Which object encapsulates state or data of a user?
Answer:
Session object.

Question 79.
What are the differences between the Response.Write() and Response.Output.Write()?
Answer:
Response.Write( ) is used for normal output whereas Response.Output.Write() is used for formatted output.

Question 80.
Define the types of configuration files.
Answer:
There are two types of configuration files:

Application Level config = Web.config.
Machine Level config = Machine.config.

Question 81.
What is the difference between Web config and Machine config files?
Answer:
Web config file is specific to web application whereas Machine config file is specific to machine or server.
There can be multiple web config files in an application but only one machine config file.

Question 82.
What are the HTML server controls in ASP.NET?
Answer:

HTML server controls are just like HTML elements that we use on HTML pages.
HTML server controls are used to expose properties and events for use.
To make these controls programmatically accessible, we specify that the HTML controls act as a server control by adding the runat=Mserver” attribute.

Java swing interview questions – Abstract Windows Toolkit (AWT) Interview Questions in Java

September 6, 2022 by Prasanna

Java swing interview questions: List of topic-wise frequently asked java interview questions with the best possible answers for job interviews.

Abstract Windows Toolkit (AWT) Interview Questions in Java

Question 1.
What is meant by controls and what are the different types of controls in AWT?
Answer:
Controls are components that allow a user to interact with your application and the AWT supports the following types of controls:
Labels, Push Buttons, Check Boxes, Choice Lists, Lists, Scrollbars, Text Components. These controls are subclasses of Component.

Question 2.
What is the difference between choice and list?
Answer:
A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices and only one item may be selected from a choice. A-List may be displayed in such a way that several List items are visible and it supports the selection of one or more list items.

Question 3.
What is the difference between scrollbar and scrollpane?
Answer:
A Scrollbar is a Component, but not a Container whereas Scrollpane is a Container and handles its own events and performs its own scrolling.

Question 4.
What is a layout manager and what are the different types of layout managers available in java.awt?
Answer:
A layout manager is an object that is used to organize components in a container. The different layouts are available are FlowLayout, BorderLayout, CardLayout, GridLayout, and GridBagLayout.

Question 5.
How are the elements of different layouts organized?
Answer:
FlowLayout: The elements of a FlowLayout are organized in a top to bottom, left to right fashion.
BorderLayout: The elements of a BorderLayout are organized at the borders (North, South, East, and West)and the center of a container.
CardLayout: The elements of a CardLayout are stacked, on top of the other, like a deck of cards.
GridLayout: The elements of a GridLayout are of equal size and are laid out using the square of a grid.
GridBagLayout: The elements of a GridBagLayout are organized according to a grid.
However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.

Question 6.
Which containers use a Border layout as their default layout?
Answer:
Window, Frame, and Dialog classes use a BorderLayout as their layout.

Question 7.
Which containers use a Flow layout as, their default layout?
Answer:
Panel and Applet classes use the FlowLayout as their default layout.

Question 8.
Why the container does not support multiple layout managers?
Answer:
because when u r using a particular layout manager it useful frame for work you can use a grid bag layout for this purpose.

Question 9.
What is clipping?
Answer:
Clipping is the process of confining paint operations to a limited area or shape.

Question 10.
What is meant by controls and what are the different types of controls in AWT?
Answer:
Controls are components that allow a user to interact with your application and the AWT supports the following types of controls:
Labels, Push Buttons, Check Boxes, Choice Lists, Lists, Scrollbars, Text Components. These controls are subclasses of Component.

Question 11.
What is the difference between choice and list?
Answer:
A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices and only one item may be selected from a choice. A-List may be displayed in such a way that several List items are visible and it supports the selection of one or more list items.

Question 12.
What is the difference between scrollbar and scrollpane?
Answer:
A Scrollbar is a Component, but not a Container whereas Scrollpane is a Container and handles its own events and performs its own scrolling.

Question 13.
What is a layout manager and what are the different types of layout managers available in java.awt?
Answer:
A layout manager is an object that is used to organize components in a container. The different layouts are available are FlowLayout, BorderLayout, CardLayout, GridLayout, and GridBagLayout.

Question 14.
What is a Layout Manager and what are the different Layout Managers available in java.awt and what is the default layout manager for the panel and the panel subclasses?
Answer:
A layout manager is an object that is used to organize components in a container. The different layouts are available in java.awt is:

• FlowLayout: The elements of a FlowLayout are organized in a top to bottom, left to right fashion.

• BorderLayout: The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container.

• CardLayout: The elements of a CardLayout are stacked, one on top of the other, like a deck of cards.

• GridLayout: The elements of a GridLayout are of equal size and are laid out using the square of a grid.

• GridBagLayout: The elements of a GridBagLayout are organized according to a grid. However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.
The default Layout Manager of Panel and Panel sub-classes is FlowLayout.

Question 15.
Which containers use a Border layout as their default layout?
Answer:
Window, Frame, and Dialog classes use a BorderLayout as their layout.

Question 16.
Which containers use a Flow layout as their default layout?
Answer:
Panel and Applet classes use the FlowLayout as their default layout.

Question 17.
Assume that g is an object belonging to the Graphics class. What image would be produced by the following commands? Draw a picture as part of your answer.
g;setColor(Color.gray);
g.fiIlRect(0,0,40,40);
g.fillRect(50,50,0,0);
g.setColor(Color.black);
g.fill0val(50,0,40,40);
g.fill0val(0,50,40,40);
Answer:
The method “g.fillRect(x,y,w,h)” draw a solid rectangle with its upper left corner at the point (x,y). The other two parameters, w, and h, give the width and height of the rectangle. In the second line “g.fillRect(50,50,0,0)” doesn’t produce any image at all, since the width and height are specified as zero. The method “g.fillOval(x,y,w,h)” draw a solid oval that just fits inside the rectangle with upper. left corner at (x,y) and with width w and height h. So, the picture produced contains one gray square and two black circles, arranged like this:
(Note: I actually meant the second fine to be “g.fillRect(50,50,40,40).” Without this typo, the picture would have another gray square.)

Question 18.
What is the use of the window class?
Answer:
The window class can be used to create a plain, bare-bones window that does not have a border or menu. The Window class can also be used to display introduction or welcome screens.

Question 19.
What are the benefits of Swing over AWT?
Answer:
Swing components are lightweight. We can have a pluggable look & feel feature that shows us how they appear on other platforms. We can add images to Swing components. We have toolbars and tooltips in Swing.

Question 20.
Where the CardLayout is used?
Answer:
Card Layout is used where we need to have a bunch of panels or frames one laying over another. It is replaced by TabbedPane in Swing.

Question 21.
What is the difference between Grid and GridbagLayout?
Answer:
In Grid layout, the size of each grid is constant whereas in GridbagLayout grid size can Vareid.

Question 22.
How will you add a panel to a Frame?
Answer:
Frame.add(panel,BorderLayout.NORTH) or Frame.add(panel,’’North”).

Question 23.
What is the use of the window class?
Answer:
The window class can be used to create a plain, bare-bones window that does not have a border or menu. The Window class can also be used to display introduction or welcome screens.

Question 24.
What is the difference between a Window and a Frame?
Answer:
The Frame class extends Window to define the main application window that can have a menu bar.

Question 25.
What is the difference between the Font and FontMetrics classes?
Answer:
The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object.

Question 26.
For which statements does it make sense to use a label?
Answer:
The only statements for which it makes sense to use a label are those statements that can enclose a break or continue statement.

Question 27.
Which TextComponent method is used to set a TextComponent to the read-only state?
Answer:
setEditable( )

Question 28.
How are the elements of a CardLayout organized?
Answer:
The elements of a CardLayout are stacked, one on top of the other, like a deck of cards.

Question 29.
What advantage do Java’s layout managers provide over traditional windowing systems?
Answer:
Java uses layout managers to layout components in a consistent manner across all windowing platforms. Since Java’s layout managers aren’t tied to absolute sizing and positioning, they are able to accommodate platform-specific differences among windowing systems.

Question 30.
What is the difference between the paint( ) and repaint( ) methods?
Answer:
The paint( ) method supports painting via a Graphics object. The repaint( ) method is used to cause paint( ) to be invoked by the AWT painting thread.

Question 31.
Which class is the immediate superclass of the Container class?
Answer:
Component

Question 32.
How can the Checkbox class be used to create a radio button?
Answer:
By associating Checkbox objects with a CheckboxGroup.

Question 33.
Name four Container classes.
Answer:
Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane

Question 34.
What Checkbox method allows you to tell if a Checkbox is checked?
Answer:
getState( )

Question 35.
How are the elements of a GridLayout organized?
Answer:
The elements of a GridBad layout are of equal size and are laid out using the squares of a grid.

Question 36.
Which Component subclass is used for drawing and painting?
Answer:
Canvas

Question 37.
What are the problems faced by Java programmers who don’t use layout managers?
Answer:
Without layout managers, Java programmers are faced with determining how their GUI will be displayed across multiple windowing systems and finding a common sizing and positioning that will work within the constraints imposed by each windowing system.

Question 38.
What is Double Buffering?
Answer:
Double Buffering is a technique used to achieve smooth animations in Canvases or Panels. It is memory and CPU-consuming but is unavoidable as soon as you want to animate something. This technique is not applicable for native components like Buttons, Lists, etc… Since the redisplay is handled by the underlying toolkits (Motif or MsWin).

To handle double buffering, one must first draw the widget’s contents in an off¬screen image and then transfer the contents of the image to the visible window.

class DoubleBufferedcanvas extends Canvas {

    public void update(Graphics g) {
    Graphics offgc;
    Image offscreen = null;
    Dimension d = size( );

    // create the offscreen buffer and associated Graphics
    offscreen = createimage(d.width, d.height);
    offgc = off screen. getGraphics( );
    //clear the exposed area
    offgc.setColor(getBackground( ));
    offgc.fillRect(0, 0, d.width, d.height);
    offgc.setColor(getForeground( ));
    // do normal redraw
    paint(offgc);
    // transfer offscreen to window
    g.drawimage(offscreen, 0, 0, this);
   }
}

This method has one major drawback: it copies the whole buffer each time an update is required. This may consume a lot of time and CPU for a large window Hopefully, graphics contains a definition of the area that has to be redrawn: it is called clip region. The region, in Java Graphics, has two meanings:

It tells which part needs to be drawn
It clips drawing orders inside this area that means if you draw outside the clip region, nothing will appear.

Using clip regions, we can define an optimized version of the DoubleBufferedCanvas:

class OptimizedDoubleBufferedCanvas extends canvas {

   public void update(Graphics g) {
   Graphics offgc;
   Image offscreen = null;
   Rectangle box = g.getclipRect( );

   // create the offscreen buffer and associated Graphics
   offscreen = createimagefbox.width, box.height);
   offgc = offscreen.getGraphics( ));
   // clear the exposed area
   offgc.setcolor(getBackg round( ));
   offgc.fillRect(0, 0, box.width, box.height);
   offgc.setcolor(getForeground( ));
   // do normal redraw
   offgc.translateC-box.x, -box.y);
   paint(offgc);
   // transfer offscreen to window
   g.drawlmage(offscreen, box.x, box.y, this);
   }
}

Question 39.
What is the preferred size of a component?
Answer:
The preferred size of a component is the minimum component size that will allow the component to display normally.

Question 40.
What method is used to specify a container’s layout?
Answer:
The setLayout( ) method is used to specify a container’s layout.

Question 41.
Which containers use a FlowLayout as their default layout?
Answer:
The Panel and Applet classes use the FlowLayout as their default layout.

Question 42.
Name Component subclasses that support painting.
Answer:
The Canvas, Frame, Panel, and Applet classes support painting.

Question 43.
Can an anonymous class be declared as implementing an interface and extending a class?
Answer:
An anonymous class may implement an interface or extend a superclass, but may not be declared to do both.

Question 44.
Which Container method is used to cause a container to be laid out and redisplayed?
Answer:
validate( )

Question 45.
What is the difference between a Window and a Frame?
Answer:
The Frame class extends Window to define the main application window that can have a menu bar.

Question 46.
What do heavy-weight components mean?
Answer:
Heavyweight components like Abstract Window Toolkit (AWT), depending on the local windowing toolkit. For example, java.awt.The button is a heavy-weight component, when it is running on the Java platform for Unix platform, it maps to a real Motif button. In this relationship, the Motif button is called the peer to the java.awt.Button. If you create two Buttons, two peers and hence two Motif Buttons are also created. The Java platform communicates with the Motif Buttons using the Java Native Interface. For each and every component added to the application, there is an additional overhead tied to the local windowing system, which is why these components are called heavyweight.

Question 47.
How are the elements of a GridBagLayout organized?
Answer:
The elements of a GridBagLayout are organized according to a grid. However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.

Question 48.
What advantage do Java’s layout managers provide over traditional windowing systems?
Answer:
Java uses layout managers to layout components in a consistent manner across all windowing platforms. Since Java’s layout managers aren’t tied to absolute sizing and positioning, they are able to accommodate platform-specific differences among windowing systems

Question 49.
What is the difference between the paint( ) and repaint( ) methods?
Answer:
The paint( ) method supports painting via a Graphics object. The repaint( ) method is used to cause paint( ) to be invoked by the AWT painting thread.

Question 50.
Name Container classes.
Answer:
Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane

Question 51.
What is the difference between a Scrollbar and a ScrollPane?
Answer:
A Scrollbar is a Component, but not a Container. A ScrollPane is a Container. A ScrollPane handles its own events and performs its own scrolling.

Question 52.
What is a Container in a GUI?
Answer:
A Container contains and arranges other components (including other containers) through the use of layout managers, which use specific layout policies to determine where components should go as a function of the size of the container.

Question 53.
How to add a menu shortcut to menu items?
Answer:
If you have a button instance called the about the button, you may add a menu shortcut by calling the about button.setMnemonic(A.’), so the user may be able to use Alt+A to click the button.

Question 54.
What is the difference between Swing and AWT components?
Answer:
AWT components are heavy-weight, whereas Swing components are lightweight. Heavyweight components depend on the local windowing toolkit. For example, java.awt.The button is a heavy-weight component, when it is running on the Java platform for Unix platform, it maps to a real Motif button.

Question 55.
What is meant by controls and what are the different types of controls?
Answer:
Controls are components that allow a user to interact with your application. The AWT supports the following types of controls:
Labels, Pushbuttons, Checkboxes, Choice lists, Lists, Scroll bars, Text components These controls are subclasses of Component.

Question 56.
How can we get all public methods of an object dynamically?
Answer:
By using
get methods( ): It returns an array of method objects corresponding to the methods of this class.
getFields( ): It returns an array of Filed objects corresponding to the Fields(variables) of this class.
getConstructors( ): It returns an array of constructor objects corresponding to public constructors of this class.

Question 57.
What is the SubClass of Text component Class?
Answer:
TextField and TextArea

Question 58.
Which method of the Component class is used to set the position and the size of a component?
Answer:
setBounds( )

Question 59.
Which TextComponent method is used to set A TextComponent to the read¬only state?
Answer:
setEditable( )

Question 60.
How can the Checkbox class be used to create a radio button?
Answer:
By associating Checkbox objects with a CheckboxGroup.

Question 61.
What Checkbox method allows you to tell if a Checkbox is checked?
Answer:
getState( )

Question 62.
Which Component method is used to access a component’s immediate Container?
Answer:
getParent( )

Question 63.
What methods are used to get and set the text label displayed by a Button object?
Answer:
getLabel( ) and setLabel( )

Question 64.
What is the difference between a Choice and a List?
Answer:
A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices. Only one item may be selected from a Choice.
A-List may be displayed in such a way that several List items are visible. A-List supports the selection of one or more List items.

Question 65.
Which Container method is used to cause a container to be laid out and redisplayed?
Answer:
validate( )

Question 66.
What is the difference between a Scrollbar and a Scrollpane?
Answer:
A Scrollbar is a Component, but not a Container. A Scrollpane is a Container and handles its own events and performs its own scrolling.

Question 67.
Which Component subclass is used for drawing and painting?
Answer:
Canvas.

Question 68.
Which method is used to set the text of a Label object?
Answer:
setText( )

Question 69.
Which method will cause a Frame to be displayed?
Answer:

a) . show( )
b) . setVisible( )

Question 70.
All the component classes and container classes are derived from
class.
Answer:
Object.

Question 71.
Which method of the container class can be used to add components to a Panel?
Answer:
add ( ) method.

Question 72.
What are the subclasses of the Container class?
Answer:
The Container class has three major subclasses. They are:
Window, Panel, ScrollPane

Question 73.
Can the Choice component allow multiple selections?
Answer:
No

Question 74.
Which components are used to get text input from the user?
Answer:
TextField and TextArea.

Question 75.
Which object is needed to group Checkboxes to make them exclusive?
Answer:
CheckboxGroup.

Question 76.
What are the types of Checkboxes and what is the difference between them?
Answer:
Java supports two types of Checkboxes. They are:
Exclusive and Non-exclusive.
In the case of exclusive Checkboxes, only one among a group of items can be selected at a time. If an item from the group is selected, the checkbox currently checked is deselected and the new selection is highlighted. The exclusive Checkboxes are also called Radio buttons.
The non-exclusive checkboxes are not grouped together and each one can be selected independent of the other.

Question 77.
What is a Layout Manager and what are the different Layout Managers available in java.awt and what is the default layout manager for the panel and the panel subclasses?
Answer:
A layout manager is an object that is used to organize components in a container.

Question 78.
What are the different layouts available in java.awt :
Answer:
FlowLayout, BorderLayout, CardLayout, GridLayout, GridBag Layout. The default Layout Manager of Panel and Panel sub classes is FlowLayout”.

Question 79.
Can I exert control over the size and placement of components in my interface?
Answer:
Yes.

Question 80.
Can I add the same component to more than one container?
Answer:
No. Adding a component to a container automatically removes it from any previous parent (container).

Question 81.
How do I specify where a window is to be placed?
Answer:
Use setBounds, setSize, or setLocation methods to implement this.
setBounds(int x, int y, int width, int height)
setBounds(Rectangle r)
setSize(int width, int height)
setSize(Dimension d)
setLocation(int x, int y)
setLocation(Point p)

Question 82.
How can we create a borderless window?
Answer:
Create an instance of the Window class, give it a size, and show it on the screen.
Ex. Frame obj =…………………..
Window WA = new Window(obj);
WA.setLayout(new FlowLayoutO);
WA.add(new Button(“OK”));
WA.getBounds(50,50,200,200);
WA.show( );

Question 83.
Can I create a non-resizable window? If so, how?
Answer:
Yes. By using setResizable( ) method in class Frame.

Question 84.
What is the default Layout Manager for the Window and Window subclasses (Frame, Dialog)?
Answer:
BorderLayout( )

Question 85.
Which containers use a BorderLayout as their default layout?
Answer:
The Window, Frame, and Dialog classes use a BorderLayout as their default layout.

Question 86.
Which containers use a FlowLayout as their default layout?
Answer:
The Panel and the Applet classes use the FlowLayout as their default layout.

Question 87.
What is the preferred size of a component?
Answer:
The preferred size of a component size will allow the component to display normally.

Question 88.
Which method is a method to set the layout of a container?
Answer:
setLayout( )

Question 89.
Which method returns the preferred size of a component?
Answer:
getPreferredSize( )

Question 90.
Which layout should you use to organize the components of a container in a tabular form?
Answer:
GridLayout

Question 91.
What are the default layouts for an applet, a frame, and a panel?
Answer:
For an applet and a panel, Flow layout is the default layout, whereas Border layout is the default layout for a frame.

Question 92.
How can you change the current layout manager for a container?
Answer:
By using setLayout( ) method.

Question 93.
Which is the default layout for Applet?
Answer:
The default layout manager for an Applet is FlowLayout, and The FlowLayout manager attempts to honor the preferred size of any components.

Question 94.
Which method does display the messages whenever there is an item selection or deselection of the CheckboxMenuItem menu?
Answer:
itemStateChanged method.

Question 95.
Which is a dual state menu item?
Answer:
CheckboxMenuItem.

Question 96.
Which container may contain a menu bar?
Answer:
Frame

Question 97.
What is the difference between a Menultem and a CheckboxMenuItem?
Answer:
The CheckboxMenuItem class extends the Menultem class to support a menu item that may be checked or unchecked.

Question 98.
What is the correct ordering for the import, class, and package declarations when found in a single file?
Answer:
package, import, class

Question 99.
What is the parameter specification for the public static void main method?
Answer:

String args [ ]
String [ ] args

Question 100.
What is the sweep and paint algorithm?
Answer:
The painting algorithm takes as input a source image and a list of brush sizes, sweep algo is that it computes the arrangement of n lines in the plane … a correct algorithm,

Question 101.
What are the component and container classes?
Answer:
A component is a graphical object. A few examples of components are Button, Canvas, Checkbox, Choice, etc.

Question 102.
Explain the purpose of invalidating and validate methods.
Answer:
The invalidate method is called a side effect of adding or deleting some component. Calling invalidates ( ) is however the first step of processing a COMPONENTJtESIZED event.

Question 103.
What are AWT peers? When are peers created and destroyed?
Answer:
A Component is associated with a standard AWT button object, a peer object (hidden button object internal to the native GUI), and an interfacing button object constructed per the native GUI.

Question 104.
Show with an example the usage of the FileDialog object.
Answer:
class FileDialog extends from Dialog class. It is used to display a dialog window from which the user can select a file.

Question 105.
Explain the purposes of the component’s request focus method.
Answer:
The purpose of the request focus( ) is to get the focus on the particular component and also on the window that contains the component.

Question 106.
Which method of the Component class is used to set the position and size of a component?
Answer:
The methods are: set maximum size(Dimension maximum size) Sets the maximum size of this component to a constant value.

Question 107.
What interface is extended by AWT event listeners?
Answer:
The java. util.EventListener interface is extended by all the AWT event listeners.

Question 108.
What is the paint method? What should we put in the paint method? When is it invoked?
Answer:
The AWT uses a Callback mechanism for painting which is the same for heavyweight and lightweight components.

Question 109.
What is the purpose of the repaint method? When should we use the repaint method?
Answer:
repaint( ) requests can erase and redraw (update) after a small time delay. When you invoke repaint( )

Question 110.
Explain the use of the update method. When is it invoked?
Answer:
An update method is called on calling the repaint method. The default implementation of the update( ) method clears the screen and calls the paint( ) method.

Question 111.
How does the XOR drawing mode work? What are the properties of XOR j drawing?
Answer:
setXORMode(Color cl) sets the paint mode of this graphics context to alternate between a graphics context’s current color and the new specified color.

Question 112.
Explain how to load an image from the net into my applet.
Answer:
private Imagelcon image;
inside the init method
image = new ImageIcon(new URL(http://www.xyz.gif));

Question 113.
Explain how to load an image from a file in a java application.
Answer:
Imagelcon icon = createImageIcon(“images/xyz.gif’, “text string”);

Question 114.
What is the difference between a Window and a Frame?
Answer:
A frame is a resizable, movable window with a title bar and a close button. Usually, it contains Panels. It’s derived from a window and has a BorderLayout by default.

Question 115.
Explain how to draw text over a background image.
Answer:
Bufferedlmage img = ImageIO.read(new File(“xxx”)); // xxx is the path TextOnBackground test = new TextOnBackground(img);

Question 116.
Define canvas?
Answer:
It is a simple drawing surface that is used for painting images or to perform other graphical operations.

Basics of Python – Regular Expression Module

September 6, 2022 by Prasanna

In this Page, We are Providing Basics of Python – Regular Expression Module. Students can visit for more Detail and Explanation of Python Handwritten Notes Pdf.

Basics of Python – Regular Expression Module

Regular expression module

re module in python: A regular expression (also called RE, or regex, or regex pattern) is a specialized approach in Python, using which programmers can specify rules for the set of possible strings that need to be matched; this set might contain English sentences, e-mail addresses, or anything. REs can also be used to modify a string or to split it apart in various ways.

Meta characters

Most letters and characters will simply match themselves. For example, the regular expression test will match the string test exactly. There are exceptions to this rule; some characters are special “meta characters”, and do not match themselves. Instead, they signal that some out-of-the-ordinary thing should be matched, or they affect other portions of the RE by repeating them or changing their meaning. Some of the meta characters are discussed below:

Meta character	Description	Example
[ ]	Used to match a set of characters.	[time] The regular expression would match any of the characters t, i, m, or e. [a-z] The regular expression would match only lowercase characters.
∧	Used to complement a set of characters.	[^∧time] The regular expression would match any other characters than t, i, m or e.
$	Used to match the end of string only.	time$ The regular expression would match time in ontime, but will not match time in timetable.
*	Used to specify that the previous character can be matched zero or more times.	tim*e The regular expression would match strings like timme, tie and so on.
+	Used to specify that the previous character can be matched one or more times.	tim+e The regular expression would match strings like timme, timmme, time and so on.
?	Used to specify that the previous character can be matched either once or zero times.	tim ?e The regular expression would only match strings like time or tie.
{ }	The curly brackets accept two integer values. The first value specifies the minimum number of occurrences and the second value specifies the maximum of occurrences.	tim{1,4}e The regular expression would match only strings time, timme, timmme or timmmme.

Regular expression module functions

Some of the methods of re module as discussed below:

re. compile ( pattern )
The function compile a regular expression pattern into a regular expression object, which can be used for matching using its match ( ) and search ( ) methods, discussed below.

>>> import re
>>> p=re.compile ( ' tim*e ' )

re. match ( pattern, string )
If zero or more characters at the beginning of the string match the regular expression pattern, match-( ) return a corresponding match object instance. The function returns None if the string does not match the pattern.

re. group ( )
The function return the string matched by the RE.

>>> m=re .match ( ' tim*e' , ' timme pass time ' )
>>> m. group ( )
' timme '