Make it patrol

Unit 1: Meet Greenfoot · Lesson 1.6 The act() Method · code exercise, graded

What to write

1. Move the crab 2 forward every frame.
2. When it reaches the edge of the world, turn it 180 degrees so it walks back.

Your code

Press Run to watch your code on the grid. Nothing is recorded by Run, so press it as often as you like. Step goes one frame at a time, which is the view that actually explains what act() does.

What it is checked against

These are the examples you can see. There are also 2 hidden cases with different setups, so printing the answers below as text passes nothing.

World w = new World(12, 6, 32);
Harness h = new Harness();
w.addObject(h, 2, 3);
for (int i = 0; i < 4; i++)
{
h.act();
}
System.out.println(h.getX() + "," + h.getRotation());

10,0

World w = new World(12, 6, 32);
Harness h = new Harness();
w.addObject(h, 2, 3);
for (int i = 0; i < 8; i++)
{
h.act();
}
System.out.println(h.getX() + "," + h.getRotation());

5,180