NullPointerException on java array, have created new objects

Question

I'm getting a NullPointerException error when trying to run my program at this part:

File folder = new File("mypictures");
File[] pictures = folder.listFiles();
allCards = new Card[pictures.length];

for(int i=0; i < (pictures.length); i++){
    allCards[i] = new Card(new ImageIcon(pictures[i].getPath())); 
}

It complains on the follow line:

Card[] allCards = new Card[pictures.length];

listFiles() can return null. "Returns null if this abstract pathname does not denote a directory, or if an I/O error occurs." — Alexis C.
– Alexis C., Commented Feb 11, 2014 at 20:39
A NullPointerException occurs at runtime, not when compiling. — rgettman
– rgettman, Commented Feb 11, 2014 at 20:39

Mureinik · Accepted Answer · 2014-02-11 20:40:26Z

5

If folder does not refer to a directory, listFiles() will return null. I.e., when you attempt to call pictures.length, you'll fail with a NullPointerException.

answered Feb 11, 2014 at 20:40

Mureinik

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user300313 · Accepted Answer · 2014-02-11 20:50:26Z

0

Quite a few things can go wrong in your code. Please use try catch and make sure that folder exists before listing files in the folder.

answered Feb 11, 2014 at 20:50

user300313

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