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

Your equals implementation is wrong. Your in parameter should not be a String. It should be an InnerClass.

public boolean equals(Object o) {
  if (this == o) return true;
  if (!(o instanceof InnerClass) return false;
  InnerClass that = (InnerClass)o;
  // check for null keys if you need to
  return this.testKey.equals(that.testKey);
}

(Note that instanceof null returns false, so you don't need to check for null first).

You would then test for existence of an equivalent object in your list using:

objectList.contains(new InnerClass("UNIQUE ID1"));

But if you really want to check for InnerClass by String key, why not use Map instead?