Greenfoot

Question 1

How do you make an actor turn and move randomly?

Answer 1

move(Greenfoot.getRandomNumber(2));
turn(90*Greenfoot.getRandomNumber(3));

Question 2

How do you make actor move in the direction of the arrow keys when pressed?

Answer 2

if (Greenfoot.isKeyDown(“left”))
{
setLocation(getX()-1,getY());
}
if (Greenfoot.isKeyDown(“right”))
{
setLocation(getX()+1,getY());
}
if (Greenfoot.isKeyDown(“up”))
{
setLocation(getX(),getY-1());
}
if (Greenfoot.isKeyDown(“down”))
{
setLocation(getX(),getY+1());
}

Question 3

How to edit actor(1) code to make an actor(1) remove another actor(2) when it collided with it?

Answer 3

Actor collided = getOneIntersectingObject(actor(2).class);
if (collided != null)
{
getWorld().removeObject(collided);
}

Question 4

How to add a sound every time actor(1) collides with actor(2)?

Answer 4

Greenfoot.playSound(“pop.wav”);

Question 5

How to edit actor(1) code so the counter displays how many actor(2) it’s collided with?

Answer 5

((Counter)getWorld().getObjects(Counter.class).get(0)).bumpCount(1);

Question 6

What is the correct counter code?

Answer 6

private int totalCount = 0;
public Counter()
{
setImage(new GreenfootImage(“0”, 20, Color.WHITE, Color.BLACK));
}
public void bumpCount(int amount)
{
totalCount += amount;
setImage(new GreenfootImage(“” + totalCount, 20, Color.WHITE, Color.BLACK));

Question 7

How to edit actor(2) code so it removes itself if it collides with actor(3)?

Answer 7

Actor collided = getOneIntersectingObject(actor(3).class);
if (collided != null)
{
getWorld().removeObject(this);
}

Question 8

How to edit actor(2) code so that 1 point is deducted from the counter if actor(2) is removed?

Answer 8

((Counter)getWorld().getObjects(Counter.class).get(0)).bumpCount(-1);

Question 9

How to make the world class a square

Answer 9

Change the numbers in the world class’s method into:
super(9, 9, 60);

Question 10

How to make actor(2) move randomly left to right?

Answer 10

move(Greenfoot.getRandomNumber(2));
turn(180*Greenfoot.getRandomNumber(3));

Question 11

What does the term ‘superclass’ mean and examples?

Answer 11

A class which other classes inherit from, e,g. World & Actor

Question 12

What does the term ‘property’ mean?

Answer 12

A variable associated with a class, e.g. private xyz

Question 13

What does the term ‘class’ mean?

Answer 13

Representation of a real world object, e.g. cat, mouse & ground

Question 14

What does the term ‘method’ mean?

Answer 14

A function associated with a class, e.g. public xyz

Question 15

What does the term ‘comment’ mean?

Answer 15

An additional bit of information that explains what some code is doing, e.g.
/**
*xyz
*/