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Hour of Code: Build Your Robot World in Java

Loopy wanderer: loops

Explore how for-loops in Java simplify repetitive tasks by allowing you to execute code multiple times without rewriting it. This lesson helps you understand loop structures to move a robot through different directions, and challenges you to program the robot to wander randomly for 20 turns, enhancing your basic coding skills.

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Loops

To move the robot in five different directions, you probably had some code like this, repeated five times:

Java
   dir = randomGenerator.nextInt(4);
   robbie.setDirection(dir);
   maze.turn();

Is there a way to make Java do the same thing over and over again, so that we don’t have to type the same lines of code over and over again? Yes! The next code shows a programming construct called a for-loop that causes Java to execute the lines of code inside the braces of the loop 5 times:

Java
class YellowBrick {
  public static void main(String[] args) {
    for(int i = 0; i < 5; i++) {
      System.out.println("Follow the yellow brick road.");
    }
  }
}

Exercise: loopy wanderer

Write code to make the robot wander randomly for 20 turns.

Loopy wanderer
Solution
import com.educative.robot.*;
import java.util.Random;
class LoopyWanderer {
  
	public static void main(String[] args) { 
    // set up variables to store the robot and the maze
    Robot robbie;
    Maze maze;
    
    Random randomGenerator = new Random();
    int dir;
    
    // create the robot and maze, and add
    // the robot to the maze
    robbie = new Robot(3.0, 3.0, "red");
    maze = new Maze(8, 8, 50);
    maze.add(robbie);
  
    // your code here:
    
  }
}