Java Program to Find the First Digit of a Number

In the previous article, we have seen Java Program to Calculate Electricity Bill

In this article we will see how to find the first digit of a number using Java programming language.

Java Program to Find the First Digit of a Number

The digit at the beginning of a number is called as first digit.

For example:

A number is 786

So, the first digit of a number is 7.

Let’s see different ways to find the first digit of the number.

By Using Static Input Value
By Using User Input Value
By Using User Defined Method

Method-1: Java Program to Find the First Digit of a Number By Using Static Input Value

Approach:

Declare an integer variable say ‘num‘ and initialize a value.
Assign the value of ‘num‘ to a temporary value ‘temp‘
Declare an integer variable ‘totalDigit‘ and initialize it to 0.
Take a while loop and continue till ‘temp‘ value becomes 0.
Inside while loop divide ‘temp‘ by 10 and increment value of ‘totalDigit‘.
After completion while loop now ‘totalDigit‘ holds the value of total number of digits.
Then find the first digit by dividing the number with (int)Math.pow(10,totalDigit-1) means num/(int)Math.pow(10,totalDigit-1)
Print the first digit.

Program:

public class Main
{
    public static void main(String[] args) 
    {
        //a number declared
  	    int num=590;

  	    //assigning the value of 'num' to a temporary variable 'temp'
  	    int temp=num;
  	    
  	    //declaring integer variable 'totalDigit' and initializing it to 0
  	    int totalDigit=0;
  	    //while loop to find total number of digits
  	    while(temp!=0)
  	    {
  	        temp=temp/10;
  	        totalDigit++;
  	    }
    
        //find first digit of the number
  	    int firstDigit = num /(int)Math.pow(10,totalDigit-1);
        
        System.out.println("First Digit: "+ firstDigit);
 
    }
}

Output:

First digit: 5

Method-2: Java Program to Find the First Digit of a Number By Using User Input Value

Approach:

Declare an integer variable say ‘num‘ and take value as user input.
Assign the value of ‘num‘ to a temporary value ‘temp‘
Declare an integer variable ‘totalDigit‘ and initialize it to 0.
Take a while loop and continue till ‘temp‘ value becomes 0.
Inside while loop divide ‘temp‘ by 10 and increment value of ‘totalDigit‘.
After completion while loop now ‘totalDigit‘ holds the value of total number of digits.
Then find the first digit by dividing the number with (int)Math.pow(10,totalDigit-1) means num/(int)Math.pow(10,totalDigit-1)
Print the first digit.

Program:

import java.util.Scanner;

public class Main
{
    public static void main(String[] args) 
    {
        //Scanner class object created
        Scanner sc=new Scanner(System.in);
        //taking a number input from user
  	    System.out.println("Please enter a number: ");
  	    int num=sc.nextInt();
  	    //assigning the value of 'num' to a temporary variable 'temp'
  	    int temp=num;
  	    
  	    //declaring integer variable 'totalDigit' and initializing it to 0
  	    int totalDigit=0;
  	    //while loop to find total number of digits
  	    while(temp!=0)
  	    {
  	        temp=temp/10;
  	        totalDigit++;
  	    }
    
        //find first digit of the number
  	    int firstDigit = num /(int)Math.pow(10,totalDigit-1);
        
        System.out.println("First Digit: "+ firstDigit);
 
    }
}

Output:

Please enter a number: 
5893
First Digit: 5

Method-3: Java Program to Find the First Digit of a Number By Using User Defined Method

Approach:

Declare an integer variable say ‘num‘ and take value as user input.
Then call a user defined method findFirst() and pass ‘num‘ as parameter.
Inside the method assign the value of ‘num‘ to a temporary value ‘temp‘
Declare an integer variable ‘totalDigit‘ and initialize it to 0.
Take a while loop and continue till ‘temp‘ value becomes 0.
Inside while loop divide ‘temp‘ by 10 and increment value of ‘totalDigit‘.
After completion while loop now ‘totalDigit‘ holds the value of total number of digits.
Then find the first digit by dividing the number with (int)Math.pow(10,totalDigit-1) means num/(int)Math.pow(10,totalDigit-1)
Print the first digit.

Program:

import java.util.Scanner;

public class Main
{
    public static void main(String[] args) 
    {
        //Scanner class object created
        Scanner sc=new Scanner(System.in);
        //taking a number input from user
  	System.out.println("Please enter a number: ");
  	int num=sc.nextInt();
  	//calling a method findFirst()
  	findFirst(num);
    }
    
    //findFirst() method to find first digit of the number
    public static void findFirst(int num)
    {
  	//assigning the value of 'num' to a temporary variable 'temp'
  	int temp=num;
  	    
  	//declaring integer variable 'totalDigit' and initializing it to 0
  	int totalDigit=0;
        //while loop to find total number of digits
  	while(temp!=0)
  	{
  	    temp=temp/10;
  	    totalDigit++;
  	}
    
        //find first digit of the number
  	int firstDigit = num /(int)Math.pow(10,totalDigit-1);
        
        System.out.println("First Digit: "+ firstDigit);
 
    }
}

Output:

Please enter a number: 
8945
First Digit: 8

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