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null comparison

Tyler Jordan
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Joined: Nov 17, 2003
Posts: 70
I have a value in an array that has certain values that are null when I do a println command on them. I need to do an statement that compares these value to null. (either that it equals or doesn't equal null). I have tried the equals method and the operators, but neither compares the values correctly. Is this a special case in Java? How should I compare these?
Chris Harris
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Joined: Sep 21, 2003
Posts: 231
Hi Tyler,
Compare null values are null do the following instead of using the equals method:
if (ipArray[s] == null) //is null
if(ipArray[s] != null) // if not null.

You can't do:
ipArray[s].equals(null)
as there is no instance created for the value so there will not be a pointer to the object. If you do this you will get a NullPointerException if ipArray[s] is null.
Hope that helps. Let us know if you have any more problems.
Chris


SCJP 1.2, SCWCD, SCBCD
 
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subject: null comparison