# Java Program to Convert Octal to Binary

## Program to convert octal to binary

In this article we will discuss about how to convert Octal to Binary. Before jumping into the program directly, let’s first know about octal and binary.

Octal  Number :

• The number system with base 8 is generally called octal number system .
• This number system us usually consists of 8 digits i.e., 0,1,2,3,4,5,6,7
• Example – (156)8 where “8” represents the base and “156” represents the octal.
• But (186)8 will be a wrong representation because the digits are possible between 0 to 7.

Binary Number :

• The number system with base 2 is generally called binary number system .
• This number system is usually consisting of 2 digits only i.e., 0 or 1 .
• Whenever there is a low voltage, it represents as 0 .
• Whenever there is a high voltage, it represents as 1 .
• Example – (10111)2 where “2” represent the base and “10111” represent the binary number.

When we convert the octal value to the binary value, we can convert by using 3-bit representation. Usually, to represent a digit in octal in binary we need at least 3 bit. Lets see how the 8 bits are represented.

Digit=0 , Then Binary representation=000
Digit=1 , Then Binary representation=001
Digit=2 , Then Binary representation=010
Digit=3 , Then Binary representation=011
Digit=4 , Then Binary representation=100
Digit=5 , Then Binary representation=101
Digit=6 , Then Binary representation=110
Digit=7 , Then Binary representation=111

Lets take a example to convert the octal to binary

(55)8 = For first 5 we represent 101 and For second 5 we represent 101

So combinedly we can write  101101

Which can also be written as (101101)2

Let’s see different ways to do it.

### Method 1 : Using switch case

Approach :

• Take an octal value as the input.
• Take each possible value with the help of switch case .
• Combine it each time with a sting and Store it into a variable .
• Print the result .

Program:

Let’s see the program to understand it more clearly.

import java.util.Scanner;
public class Main
{
public static void main(String[] args)
{
// creating scanner object
Scanner sc = new Scanner(System.in);
// input a  octal value as a string  through scanner class
System.out.println("Enter a octal Value : ");
String input1=sc.next();
int a=0;
String output = "";
// iterating the complete length of octal string and assigning the equivalent binary value  for each octal digit
while (a < input1.length())
{
// storing character according  to the number of iteration
char c = input1.charAt((int)a);
//   check all  possible 8 conditions
switch (c)
{
case '0':
output += "000";
break;
case '1':
output += "001";
break;
case '2':
output += "010";
break;
case '3':
output += "011";
break;
case '4':
output += "100";
break;
case '5':
output += "101";
break;
case '6':
output += "110";
break;
case '7':
output += "111";
break;
default:
System.out.println("\nInvalid Octal Digit "  + input1.charAt((int)a));
break;
}
a++;
}
System.out.println("Converted binary is :"+output);
}
}


Output :

Enter a octal Value : 55
Converted binary is :101101

### Method 2 : Using mathematical strategy

Approach :

• Take a octal value as the input .
• Take a for loop to iterate each digits of octal value and multiply with the power of 8 according to there position .
• Each time store it into a intermediate variable .
• Now convert the decimal value to its binary equivalent .
• Print the result .

Program :

Let’s see the program to understand it more clearly.

 import java.util.Scanner;
public class Main
{
public static void main(String[] args)
{
// creating scanner object
Scanner sc = new Scanner(System.in);
// input a  octal value as a string  through scanner class
System.out.println("Enter a octal Value : ");
int input1=sc.nextInt();
int i = 0;
int decimal= 0;
int output = 0;
while (input1 != 0)
{
decimal += (input1 % 10) * Math.pow(8, i);
++i;
input1 /= 10;
}

i = 1;
// converting generated decimal number to its binary equivalent
while (decimal!= 0)
{
output += (decimal % 2) * i;
decimal /= 2;
i *= 10;
}
System.out.println("Converted binary is :"+output);
}
}


Output :

Enter a octal Value : 55
Converted binary is :101101

### Method 3 : Using built in function

Approach :

• Take a octal value form the input .
• Convert it into its decmal value by using Integer.parseInt(input value , 8) and store it into a variable
• Now again convert it using another buit in function Integer.toBinaryString( ) Store it into a variable .
• Print the result .

Program :

Let’s see the program to understand it more clearly.

import java.util.Scanner;
public class Main
{
public static void main(String[] args)
{
// creating scanner object
Scanner sc = new Scanner(System.in);
// input a  octal value as a string  through scanner class
System.out.println("Enter a octal Value : ");
String input1=sc.next();
int octal = Integer.parseInt(input1, 8);
String output = Integer.toBinaryString(octal);
System.out.println("Converted binary is :"+output);
}
}


Output :

Enter a octal Value : 55
Converted binary is :101101