Problem of the Day

Problem:

Consider the following method which models a door in a house.

public class Door
{
    private boolean isOpen;
    
    public Door()
    {
        isOpen = false;
    }
    
    public void open()
    {
        isOpen = true;
    }
    
    public void close()
    {
        isOpen = false;
    }
    
    public boolean canWalkThrough()
    {
        return isOpen;
    }
}

A Door object is created with the instruction

Door kitchenDoor = new Door();

Which instruction(s) will open kitchenDoor?

1. kitchenDoor.open();
2. Door.open();
3. kitchenDoor.isOpen = true;

1. I only
2. II only
3. III only
4. I and II only
5. I and III only

Show solution: