ArrayList not using the overridden equals

Question

I\'m having a problem with getting an ArrayList to correctly use an overriden equals. the problem is that I\'m trying to use the equals to only test for a single key field, and

Answer 1

Although not answering your question, many Collections use hashcode(). You should override that too to "agree" with equals().

Actually, you should always implement both equals and hashcode together, and they should always be consistent with each other. As the javadoc for Object.equals() states:

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Specifically, many Collections rely on this contract being upheld - behaviour is undefined otherwise.