It's important for a program to be able to do things repeatedly; for example, a robot must read its sensors repeatedly and react only when certain conditions are met.

1. Create a new project folder named LoopExample
2. Open the LoopExample folder
3. Create a new file (File->New File)
4. Cut and paste the following program into the editor:

   public class LoopExample {
       public static void main(String args[]) {
           int counter;  
   
           counter = 1;
           while (counter <= 10) {
               System.out.println(counter);
               counter = counter + 1;
           }
       }
   }
   

5. Save the program as LoopExample.java
6. Run the program in the debugger with a breakpoint set at the line while (counter <= 10)
7. Step through the program a line at a time, observing the program output, variables, and flow of execution

Understanding the program

Our program:

1. Creates a loop counter variable
2. Initializes the loop counter to 1
3. Repeatedly evaluates the expression (counter <= 10) and while the expression evaluates as true
   1. prints the counter value
   2. increments the counter value by 1

The result of running the program is that the numbers 1 through 10 are printed. With only 10 iterations of the loop, you might ask whether it might be easier to just print each number manually, but consider a loop that might require thousands of iterations or that might run indefinitely until something happened:

    while (distanceToTarget > 0) {
       driveForward(0.50);
       distanceToTarget = checkDistance();
    }

Java includes three types of loop statements:

• while
• for
• do

Extra credit

• Read more about ​Java loops
• Re-write the sample program using a do loop
• Re-write the sample program using a for loop