While loop in java

While-loop: Used to execute a block of instructions repeatedly as long as the given condition is valid.

Syntax:

while (condition)
{
	Logic….
}

Flow-Chart:

The code executes infinite times as condition always true:

class Test 
{
	public static void main(String[] args) 
	{
		while(true)
		{
			System.out.println("Never stops");
		}
	}
}

Compiler raises error when we try define unreachable statements:

class Test 
{
	public static void main(String[] args) 
	{
		while(true)
		{
			System.out.println("Never stops");
		}
		System.out.println("Unable to reach");  // Error : 
	}
}

Another example: Directly we cannot specify the boolean type to execute loops

class Test 
{
	public static void main(String[] args) 
	{
		while(false)
		{   // Error : 
			System.out.println("Unable to reach");
		}
	}
}

We can specify the condition (boolean value) indirectly with variables to avoid compiler checking:

class Test 
{
	public static void main(String[] args) 
	{
		boolean val = false ;
		while(val)
		{  
			System.out.println("Unable to reach");
		}
		System.out.println("Ends here");
	}
}

Print 1 to 10 using while loop:

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

Print 10 to 1 using while loop:

class Loops
{
	public static void main(String[] args) 
	{
		int i=10;
		while(i>=1)
		{
			System.out.println("i val : " + i);
			--i;
		}
	}
}

Even numbers from 1 to 10:

class Test 
{
	public static void main(String[] args) 
	{
		int i=1 ;
		while(i <= 10)
		{
			if(i%2==0){
				System.out.println("Val : " + i);
			}
			++i;
		}
	}
}