Loops

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)

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;

        }

    }

}

4. 
   

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