adding value objects to set problem

I am not able to add value objects to a set. There is error message with hashcode. I do overwrite the hashcode function like this:public int hashCode() {return getId().hashCode()^31;}

[211 byte] By [mm68a] at [2007-11-26 17:08:30]

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# 1

What is the error?Why aren't you just returning the id's hashcode?

zadoka at 2007-7-8 23:36:21 >

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# 2

what hashcode should I return though?

mm68a at 2007-7-8 23:36:21 >

# 3

I tried just return getId().hashcode(). Same error:hashCode(TransferVO.java:139)at java.util.HashMap.hash(HashMap.java:263)at java.util.HashMap.put(HashMap.java:378)at java.util.HashSet.add(HashSet.java:192)

mm68a at 2007-7-8 23:36:21 >

# 4

What is the error? NullPointerException? Is getId returning null?

doremifasollatidoa at 2007-7-8 23:36:21 >

# 5

yeah.

mm68a at 2007-7-8 23:36:21 >

# 6

> yeah.Well, you can't call a method on null. That is why you are getting the NullPointerException.

zadoka at 2007-7-8 23:36:21 >

# 7

i hope you are also aware that ^ is xor not raise to power.

mkoryaka at 2007-7-8 23:36:21 >

# 8

You can't invoke hashCode() on getId() when it is null.

change the hashCode() method implementation like this:

public int hashCode() {

Object o = getId();

if ( o == null) {

return -1;

else

return o.hashCode();

}

Message was edited by:

I_LOVE_JAVA

I_LOVE_JAVAa at 2007-7-8 23:36:21 >

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