NullPointerException in my code but can't figure out why

Question

I'm writing a program for my school assignment using CardLayout() but I keep getting a null pointer error but I can't figure out why. Can someone please point out the error in my code. The code is incomplete but applet opens and displays buttons but not the card.

The error I get is when I press the Input button (so it's in the ActionListener):

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException at BookCentre.actionPerformed(BookCentre.java:162)

//removed code since assignment is due in a week.

what's on line 162 in your code? I'd imagine it's that you never initialize CardDeck1. I don't see that anywhere in the class — mike, Mar 08 '17 at 22:00

sirandy · Accepted Answer · 2017-03-08T22:15:31.140

0

The problem is -as @mike suggest- that CardDeck1 variable is never initialized. I initialize it in the declaration only for testing purposes, you must do it in the neccesary part of the code, where you really need it.

    //Only for testing purposes
    // Create JPanel deck and add cards to it
    deck = new JPanel();
    CardDeck1 = new CardLayout();
    deck.setLayout(CardDeck1);
    deck.add(inputCard(), INPUT);

Result:

edited Mar 08 '17 at 22:15

answered Mar 08 '17 at 22:09

sirandy

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Oh such a simple error. Thanks so much! This error gave me a headache for two days. – tee Mar 08 '17 at 22:42
Nice to hear it works for you!! Greetings since Mexico City! – sirandy Mar 08 '17 at 22:45

NullPointerException in my code but can't figure out why

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