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Integer to int null pointer exception?
By Jeremy | March 20, 2009
As I was coding up some stuff for class today I was using your friendly HashMap in Java. I created the hash map so it would use an Object and an Integer. I would have rather done an int but you can’t template ints. Anyway, at one point I was pulling the Integer out of the map with something like this:
int parent = map.get(parentObj);
There happened to be a case where the parent object wasn’t in the map and that line kept throwing a null pointer exception. After a few minutes, I realized that is because the conversion from Integer to int implies an implicit method call. And when the value returned from .get was null, there was a null pointer exception on the Integer.toInt() method. So beware of implicit calls.
Topics: bugs, school | No Comments »
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