For Loops in Java

A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times. 

Syntax

The syntax of a for loop is:

for(initialization; Boolean_expression; update) {
   //Statements
}

Here is the flow of control in a for loop :-

  • The initialization step is executed first, and only once. This step allows you to declare and initialize any loop control variables. and this step ends with a semi colon (;)

  • Next, the Boolean expression is evaluated. If it is true, the body of the loop is executed. If it is false, the body of the loop will not be executed and control jumps to the next statement past the for loop.

  • After the body of the for loop gets executed, the control jumps back up to the update statement. This statement allows you to update any loop control variables. This statement can be left blank with a semicolon at the end.

  • The Boolean expression is now evaluated again. If it is true, the loop executes and the process repeats (body of loop, then update step, then Boolean expression). After the Boolean expression is false, the for loop terminates.

Example :

Create a file with name "Forloop.java" and use below code :-

public class Forloop {

   public static void main(String args[]) {

      for(int x = 1; x < 20; x = x+1) {
          
         System.out.print("value of x : " + x );
         System.out.print("\n");
         
      }
   }
}

Compile it and Run :-

c:\java>javac Forloop.java
c:\java>java Forloop

Example with java.util.Scanner - User Input

Create a file with name "ScannerForLoop.java"

import java.util.Scanner;

public class ScannerForLoop
{
    public static void main( String[] args )
    {
        Scanner keyboard = new Scanner(System.in);

        System.out.println( "Type in a message, and I'll display it five times." );
        System.out.print( "Message: " );
        String message = keyboard.nextLine();

        for ( int n = 1 ; n <= 5 ; n = n+1 )
        {
            System.out.println( n + ". " + message );
        }

    }
}
Compile it and Run :-
c:\java>javac ScannerForloop.java
c:\java>java ScannerForloop

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