Exception in thread "Timer-0" java.lang.NullPointerException

Question

I have the code below,and it shows me an exception which is: Exception in thread "Timer-0" java.lang.NullPointerException. The erros is in line : jLabel1.setIcon(black); If I delete this line,then it works well. Any idea? Thank you !

Icon black=createImageIcon("black.PNG");

protected static ImageIcon createImageIcon(String path) {
    java.net.URL imgURL = Frame1.class.getResource(path);
    if (imgURL != null) {
        return new ImageIcon(imgURL);
    } else {
        System.err.println("Couldn't find file: " + path);
        return null;
    }
}

public Frame1(int seconds) {
    timer = new Timer();
    timer.schedule(new RunMeTask(), 1000,1000);
    }


 public class RunMeTask extends TimerTask {
    public int k=0;

public void run() {
    System.out.println("Run Me ~");
            jLabel1.setIcon(black);    //error
            k++;
            if (k==10) {
              timer.cancel();
            }
}
}

public static void main(String args[]) {
    new Frame1(1);
    System.out.format("Task scheduled.%n");
java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new Frame1().setVisible(true);
        }
    });
}

You havent shown us the code where jLabel1 and black are decalred. — Deadron, Nov 19 '13 at 19:47
@Deadron I edit my post and you can see where I have declared black icon. — user2933161, Nov 19 '13 at 19:51
@user2933161 Here are two possibilities. **1.** `jLabel1` is not initialized **2.** `createImageIcon` return `null` if `imgURL` is null. Make sure you have provided correct file path and file name. — Smit, Nov 19 '13 at 19:58
@Smit createImageIcon has a println() and it is not show me that it can't find a file,so it is ok at this part. How can I initialize the jlabel ? I did what I do anytime I use a jlabel. :/ — user2933161, Nov 19 '13 at 20:10
@user2933161 YOu have to initialized somewhere correct place in your code like `JLabel jLabel1 = new JLabel()`. If you dont do `new XXX` then it will be `null` by default. For more details see [`--> Creating Objects — Smit, Nov 19 '13 at 20:21
Sorry to all,I found the error. I forget to use initComponents(); in public Frame1() . Thank you ! — user2933161, Nov 19 '13 at 20:23

DoubleDouble · Answer 1 · 2013-11-19T20:05:04.800

0

Code either doesn't know what jLabel1 is, or it doesn't know what black is. Make sure both are Objects within view of that run() method.

edited Nov 19 '13 at 20:05

answered Nov 19 '13 at 19:48

DoubleDouble

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This isn't a compiler error. `NullPointerExceptions` show up when you run the program, indicating that everything compiled fine. The problem is that `jLabel1` hasn't been initialized. – musical_coder Nov 19 '13 at 19:53
@musical_coder Can you help me? Where is the error exactly? I don't understand. Thank you ! – user2933161 Nov 19 '13 at 19:56
Sorry, edited my wrong wordage. Here is what I would do to try and see what is happening: 1. set a println() in the createImageIcon method to make sure it is being called. (and that "Couldn't Find File" is not showing up) 2. set a debug marker on the line where the error is happening. – DoubleDouble Nov 19 '13 at 20:04
Also, make sure `Icon black=createImageIcon("black.PNG");` happens before `jLabel1.setIcon(black);` – DoubleDouble Nov 19 '13 at 20:08
@DoubleDouble createImageIcon has a println() and it is not show me that it can't find a file,so it is ok at this part.. – user2933161 Nov 19 '13 at 20:09
Most likely jLabel1 is not initialized. If you are already calling `JLabel jLabel1` or something similar elsewhere, try doing `jLabel1 = new JLabel()` to see if the error is still thrown. – DoubleDouble Nov 19 '13 at 20:11
@DoubleDouble Sorry,I found the error. I forget to use initComponents(); in public Frame1() . Thank you ! – user2933161 Nov 19 '13 at 20:51

Exception in thread "Timer-0" java.lang.NullPointerException

1 Answers1