CODEWITHSUNDEEP
javanullpointerexception
KisnardOnline
KisnardOnline

Reputation: 740

NullPointerException that should not occur

I am sorry to post that in case it is just something stupid I am doing, but I hope there is some weird Java thing causing this that I am unaware of and can that will help others. Am I overlooking something here? Why the NPE?

Here is my code:

SwingUtilities.invokeLater(new Runnable() {
    @Override
    public void run() {
        int itemSoldCount = Integer.parseInt(afterAt[1]);
        System.out.println("itemSoldCount: " + itemSoldCount);
        ShopJInternalFrame.shopHolderWAIType = new JLabel[itemSoldCount];

        int i = 2;
        for (int k = 0; k < itemSoldCount; k++){
            String waiType = afterAt[i];
            System.out.println("ShopJInternalFrame.shopHolderWAIType.length: " + ShopJInternalFrame.shopHolderWAIType.length);
            System.out.println("waiType: " + waiType);
            System.out.println("k: " + k);
            ShopJInternalFrame.shopHolderWAIType[k].setText(waiType);  //line 530

Here is my output:

itemSoldCount: 2
ShopJInternalFrame.shopHolderWAIType.length: 2
waiType: A
k: 0
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at com.jayavon.game.client.MyCommandReceiver$8.run(MyCommandReceiver.java:530)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$200(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

Upvotes: 0

Views: 81

Answers (2)

Kishore
Kishore

Reputation: 839

ShopJInternalFrame.shopHolderWAIType[k] will be null because you have not allocated any memory for individual array member. So you need to do this before you use the array member.

ShopJInternalFrame.shopHolderWAIType[k] = new new JLabel();

Upvotes: 0

Jim Garrison
Jim Garrison

Reputation: 86744

ShopJInternalFrame.shopHolderWAIType = new JLabel[itemSoldCount];

This allocates storage for the array, but not for any JLabel objects. The array contains all nulls at this point. When you reach 

ShopJInternalFrame.shopHolderWAIType[k].setText(waiType);

shopHolderWAIType[k] is null.

Upvotes: 5

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