Core Java

There may be a situation when we need to execute a block of code several number of times, and is often referred to as a loop. Java has very flexible three looping mechanisms.

1. While Loop

A while loop is a control structure that allows you to repeat a task a certain number of times.

Syntax:

while(Boolean_expression) {
//Statements
}

When executing, if the boolean expression result is true then the actions inside the loop will be executed. This will continue as long as the expression result is true.

public class ForLoopExample {
  public static void main(String args[]) {
    int a = 1;
    while( a < 10 ) {
      System.out.println("value of a : " + a );
      a++;
    }
  }
}

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2. Do-While Loop

The DO … WHILE loop is almost similar to the WHILE loop, the difference is that in this loop, the execution of statements occur before checking of a condition.

Syntax:

do {
//Statements
}while(Boolean_expression);

do…while loop checks the value of the loop control variable at the bottom of the loop after one repetition has occurred.

public class DoWhileLoop {  
    public static void main(String[] args) {  
        int i =10;  
        do{  
            i=i+10;  
            System.out.println("Loop Counter Variable=" +i);              
        }while (i<10);            
    }    
}

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3. For Loop

For Loop checks the condition and executes the set of the statements , It is loop control statement in java. It contain the following statements such as “Initialization” , “Condition” and “Increment/Decrement” statement

Syntax:
for(initialization; Condition; update)
{
//Statements
}

public class ForLoopExample{
    public static void main(String args[])
    {
        for(int i=0;i<10;i++)
        {
            System.out.println("Hello");
        }	
    }	
}

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