CODEWITHSUNDEEP
java
Karl Kuusik
Karl Kuusik

Reputation: 67

What's the difference between these two bits of code?

I cannot understand why one of the following bits of code compiles and the other one doesn't.

The one that doesn't compile (Compiler says the method KeyBidings() needs a return type):

public KeyBidings(){
    Action rightAction = new AbstractAction(){
        public void actionPreformed(ActionEvent e){
            x+=10;
            drawPanel.repaint();
        }
    };
    Action leftAction = new AbstractAction(){
        public void actionPreformed(ActionEvent e){
            x-=10;
            drawPanel.repaint();
        }
    };

        InputMap inputMap = drawPanel.getInputMap(JPanel.WHEN_IN_FOCUSED_WINDOW);
        ActionMap actionMap = drawPanel.getActionMap();

    inputMap.put(KeyStroke.getKeyStroke("RIGHT"), "rightAction");
    actionMap.put("rightAction", rightAction);
    inputMap.put(KeyStroke.getKeyStroke("LEFT"), "leftAction");
    actionMap.put("leftAction", leftAction);

    add(drawPanel);
    pack();
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize(640, 480);
    setTitle("Game");
    setLocationRelativeTo(null);
    setVisible(true);
}

And the one that compiles just fine:

public KeyBidings(){
    Action rightAction = new AbstractAction(){
        public void actionPerformed(ActionEvent e) {
            x +=10;
            drawPanel.repaint();
        }
    };

        InputMap inputMap = drawPanel.getInputMap(JPanel.WHEN_IN_FOCUSED_WINDOW);
        ActionMap actionMap = drawPanel.getActionMap();

    inputMap.put(KeyStroke.getKeyStroke("RIGHT"), "rightAction");
    actionMap.put("rightAction", rightAction);

    add(drawPanel);

    pack();
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setLocationRelativeTo(null);
    setVisible(true);
}

EDIT: I didn't know the difference between a constructor and a method, but now i have another problem: https://gyazo.com/cd3c21a8562589451814903febaf89fe

What's the problem here? I've included the source codes for both classes below.

Source Code 1: http://pastebin.com/vwNtJZEG Source Code 2: http://pastebin.com/nL4SbtkM

Upvotes: 0

Views: 80

Answers (1)

JB Nizet
JB Nizet

Reputation: 692231

The second one is the constructor of a class named KeyBidings, whereas the first one is a method, with a missing return type, of some other class.

Read the tutorial about constructors.

Note that the compiler doesn't say that the method may not be public, as your title says. It says that it must have a return type. That's quite different.

Upvotes: 2

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