Turtle Graphics with Java

Bern University of Teacher Education  
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while-structure (Iteration)

To draw a square with the Turtle in the first example Tu1, the programer had to repeat the two lines
joe.forward (100);
joe.right (90);

four times.
A more elegant solution is the Java program structure of the Iteration (Repetition). One or more condotions are set and the following actions are executed as long as the conditions are meet.

Run this example (Tu2.java)

// Tu2.java
import ch.aplu.turtle.*;

class Tu2
{
  Turtle joe = new Turtle();

  Tu2()
  {
    int i = 0;            //Starting value
    while (i < 4)         //Condition
    {
      joe.forward(100);   //Actions
      joe.right(90);
      i++;                //Increasing starting value
    }
  }

  public static void main(String[] args)
  {
    new Tu2();
  }
}

 

Test this example in the Online-Editor

 

Explaining the program code:
i++
is equal to i = i + 1. The value of i is increased by 1 after each repetition.

Exercises