TEST JAVA

final HelloWorld hello = new HelloWorld();
getWorld().addObject(hello, x, y); // replace x,y with adequate position
hello.printHello();

public void act() {
        if (Greenfoot.mouseClicked(btn01) || getObjects(HelloWorld.class).isEmpty()) {
            ?????????            
        }
    }

// fields for actors
private Actor btn01, btn02, mouseOn;
private Actor hello, noArg;

// constructor code to add create and add actors into world
btn01 = getNewButton("BUTTON 01");
btn02 = getNewButton("BUTTON 02");
hello = new HelloWorld();
noArg = new ConstructorNoArg();
addObject(btn01, 1050, 50);
addObject(btn02, 1050, 100);
addObject(hello, ???, ??); // wherever
addObject(noArg, ???, ??); // wherever

// act code to detect clicks on buttons
if (Greenfoot.mouseClicked(btn01)) hello.printHello();
if (Greenfoot.mouseClicked(btn02)) noArg.printConstructorNoArg();

public /** class name here */()
{
    setImage((GreenfootImage) null);
}

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)

/**
 * Write a description of class MyWorld here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class MyWorld extends World
{
    static final Color TRANS = new Color(0,0,0,0);
    
    private Actor button;
    
    private Actor btn01,btn02, btn03, btn04;
    private Actor mouseOn;
       
    private Actor helloWorld, constructorNoArg, constructorArg, constructorArgThis;
    
    /**
     * Constructor for objects of class MyWorld.
     * 
     */
    public MyWorld() {    
        // Create a new world with 600x400 cells with a cell size of 1x1 pixels.
        super(1200, 600, 1);
        
        GreenfootImage bg = getBackground();
        bg.setColor(Color.LIGHT_GRAY);
        bg.fillRect(0, 0, getWidth(), getHeight());
        bg.setColor(Color.CYAN);
        bg.fillRect(0, 0, getWidth()-300, getHeight());
        
        button = new SimpleActor();
        
        btn01 = getNewButton("LESSON 01");
        btn02 = getNewButton("LESSON 02");
        btn03 = getNewButton("LESSON 03");
        btn04 = getNewButton("LESSON 04");
        
        addObject(btn01, 1050, 50);
        addObject(btn02, 1050, 100);
        addObject(btn03, 1050, 150);
        addObject(btn04, 1050, 200);
        
        prepare();
    }
    
    public void act() {
        HelloWorld helloWorld = new HelloWorld();
        addObject(helloWorld, 425, 500);
        if (Greenfoot.mouseClicked(btn01))  helloWorld.printHello();
        
        ConstructorNoArg constructorNoArg = new ConstructorNoArg();
        addObject(constructorNoArg, 425, 500);
        if (Greenfoot.mouseClicked(btn02)) constructorNoArg.printConstructorNoArg();
        
        ConstructorArg constructorArg = new ConstructorArg("ronald", 50);
        addObject(constructorArg, 425, 500);
        if (Greenfoot.mouseClicked(btn03)) constructorArg.printConstructorArg();
        
        ConstructorArgThis constructorArgThis = new ConstructorArgThis("donald", 25);
        addObject(constructorArgThis, 425, 500);
        if (Greenfoot.mouseClicked(btn04)) constructorArgThis.printConstructorArgThis();
    }
    
    public void prepare() {
        /*System.out.println("Lesson01 : " + "Hello, World!");
        
        ConstructorNoArg constructorNoArg = new ConstructorNoArg();
        constructorNoArg.printConstructorNoArg();
        System.out.println("Lesson02 : " + constructorNoArg.name);
        
        ConstructorArg constructorArg = new ConstructorArg("ronald", 50);
        constructorArg.printConstructorArg();
        System.out.println("Lesson03 : " + constructorArg.nameOne + " " + constructorArg.ageOne);
        
        ConstructorArgThis constructorArgThis = new ConstructorArgThis("donald", 25);
        constructorArgThis.printConstructorArgThis();
        System.out.println("Lesson04 : " + constructorArgThis.name + " " + constructorArgThis.age);
        */
        
        Board board = new Board();
        addObject(board, 1050, 500);
    }
    
    protected Actor getNewButton(String caption) {
        GreenfootImage img = new GreenfootImage(200,30);
        img.fill();
        img.setColor(Color.BLUE);
        img.fillRect(3,3,194,24);
        
        GreenfootImage text = new GreenfootImage(caption,20,Color.WHITE,TRANS);
        img.drawImage(text,100-text.getWidth()/2,15-text.getHeight()/2);
        img.setTransparency(128);
        
        Actor button = new SimpleActor() {
                public void act() {
                    if (mouseOn == null && Greenfoot.mouseMoved(this)) {
                        mouseOn = this;
                        getImage().setTransparency(255);
                    }

                    if (mouseOn == this && Greenfoot.mouseMoved(null) && !Greenfoot.mouseMoved(this)) {
                        mouseOn = null;
                        getImage().setTransparency(128);
                    }
                }
            };      
        button.setImage(img);
        return button;
    }
}

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)

/**
 * Write a description of class HelloWorld here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class HelloWorld extends Actor
{
    /**
     * Act - do whatever the HelloWorld wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    
    public HelloWorld() {
        setImage((GreenfootImage) null);
    }
    
    public void printHello() {
        GreenfootImage hello = new GreenfootImage(900, 600);
        hello.setColor(Color.BLUE);
        hello.setFont(new Font("calibri", true, true, 50));
        hello.drawString("public class Hello {", 50, 100);
        hello.drawString("    public static void main(String[] args) {", 50, 140);
        hello.drawString("        System.out.println(\"Hello, World!\");", 50, 180);
        hello.drawString("    }", 50, 220);
        hello.drawString("}", 50, 260);
        setImage(hello);
    }
}

private Actor helloWorld, constructorNoArg, constructorArg, constructorArgThis;

private HelloWorld helloWorld;
private ConstructorNoArg constructorNoArg;
...

helloWorld = new HelloWorld(); // CORRECT: This uses the attribute.
HelloWorld helloWorld = new HelloWorld(); // INCORRECT: This creates a new local variable and ignores the attribute.