MouseInfo mouse;

public void act() {
    mouse = FullScreenWindow.getMouseInfo();//If the fullscreen mode is disabled Greenfoot.getMouseInfo is returned;
    //...
}

import java.awt.event.MouseEvent;
import java.awt.Point;
import java.awt.MouseInfo;

/**
 * Write a description of class FullScreenMouseInfo here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class FullScreenMouseInfo
{
    private MouseEvent mouseEvent;
    private Point mousePoint;
    
    public FullScreenMouseInfo() {
        this.mouseEvent = mouseEvent;
        mousePoint = MouseInfo.getPointerInfo().getLocation();
    }
    
    public int getButton() {
        if (mouseEvent != null) {
            return mouseEvent.getButton();
        }
        return -1;
    }
    
    public int getClickCount() {
        if (mouseEvent != null) {
            return mouseEvent.getClickCount();
        }
        return -1;
    }
    
    public int getX() {
        return (int) (mousePoint.getX() * FullScreenWorld.WORLD_WIDTH / FullScreenWindow.FRAME_WIDTH);
    }
    
    public int getY() {
        return (int) (mousePoint.getY() * FullScreenWorld.WORLD_HEIGHT / FullScreenWindow.FRAME_HEIGHT);
    }
    
    public Point getMousePoint() {
        return new Point(getX(), getY());
    }
    
    public String toString() {
        return mouseEvent.toString();
    }
}

import java.awt.event.MouseEvent;

public class GreenfootMouseListener implements java.awt.event.MouseListener {

	private FullScreenWindow window;
	
	public GreenfootMouseListener(FullScreenWindow window) {
		this.window = window;
	}
	
	@Override
	public void mouseClicked(MouseEvent e) {
		window.setMouseClicked(true);
	}

	@Override
	public void mouseEntered(MouseEvent e) {
		window.setMouseDragged(true);
	}

	@Override
	public void mouseExited(MouseEvent e) {
		window.setMouseDragged(false);
		window.setMouseDragEnded(true);
	}

	@Override
	public void mousePressed(MouseEvent e) {
		window.setMousePressed(true);
	}

	@Override
	public void mouseReleased(MouseEvent e) {
		window.setMousePressed(false);
	}
}