do while loop

A do while loop is a control structure that allows you to repeat a series of instructions over and over again. A do while loop is a post-test loop, since the boolean expression is evaluated after the loop executes once. Do while loops are especially useful if you know ahead of time that a loop should execute at least one time. For example, login screens should execute at least one time, but may require more passes through the loop if the user enters a wrong login or password.

Example:


// The following code prints out 0 1 2 3 4 done
// Here are the steps executed: 
// Step 1: int i=0;  creates a variable called i and sets the value to 0
// Step 2: Execute the instructions in the body of the loop
//             System.out.print(i+" ");
//             i++;
// Step 3: i<5 is evaluated and if true, go to step 2 
//                     if false, exit (terminate) the loop, and continue with the 
//                        next instruction after the loop body
 

int i=0;
do
{
    System.out.print(i+" ");
	i++;
} while (i<5);
System.out.print("done");	
	

// note that 2 instructions are executed each time through the loop
// the braces { } are used to block off the body of the loop



More Examples:



// prints  HelloHelloHellodone

int i=0;
do
{
   System.out.print("Hello");
   i++;
} while(i<3);
System.out.print("done");




// prints  HelloHelloHellodone

int i=1;
do
{
   System.out.print("Hello");
   i++;
} while(i<=3);
System.out.print("done");




// prints  HelloByeHelloByeHelloByedone

int i=1;
do
{
    System.out.print("Hello");
    System.out.print("Bye");
	i++;
} while(i<=3);
System.out.print("done");




// prints  
Hello
Bye
Hello
Bye
Hello
Bye
done

int i=1;
do
{
    System.out.println("Hello");
    System.out.println("Bye");
    i++;
} while(i<=3);
System.out.print("done");




// prints  
HelloBye
HelloBye
HelloBye

int i=1;
do
{
    System.out.print("Hello");
    System.out.println("Bye");
    i++;
} while(i<=3);




// prints
1  10
2  20
3  30

int i=1;
do
{
    System.out.println(i + "  " + i*10);
    i++;
} while(i<=3);