Question

Why do I get an error when I try to set the ImageIcon of this JLabel to something. It returns a null pointer exception. Does anyone know the problem?

public class Window extends JFrame{

    JPanel panel = new JPanel();
    JLabel stick[] = new JLabel[10];    

    Window(){

        super("ThisIsWindow");
        setSize(650,550);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setResizable(false);

        add(panel);
        panel.setLayout(null);

        stick[5].setIcon(new ImageIcon("stick.gif"));

    }
}

The error occurs on the last line of code that sets stick[5] to stick.gif. Can anyone help?

Answer 1

Add

stick[5] = new JLabel();

before

stick[5].setIcon(new ImageIcon("stick.gif"));

---

Basically, you are creating an array that holds 10 references of type JLabel, and those references are referring to nothing (null) at the beginning:

JLabel stick[] = new JLabel[10];

So you need to create 10 instances of JLabel with new JLabel() and let those 10 references pointing to them:

for(int i = 0; i < 10; i++) stick[i] = new JLabel();