The while loop in java executes one or more statements after testing the loop continuation condition at the start of each iteration. The do-while loop, however, tests the loop continuation condition after the first iteration has completed. Therefore, the do-while loop guarantees one execution of the loop logic whereas the while does not.
Example
public class WhileAndDoWhileLoop { public static void main(String args[]) { int i=5; System.out.println("Test while Loop:"); while(i < 5) { System.out.println("Iteration: "+ ++i); } System.out.println("Test do-while Loop:"); i=5; do { System.out.println("Iteration: "+ ++i); } while(i < 5); } }
In the above example, The while loop statement will not execute at all. However, one iteration of the do-while loop will execute.
Output
Test while Loop: Test do-while Loop: Iteration: 6