Check if an ArrayList contains a given object

Assuming I have class like this:

class A {
  int elementA;
  int elementB
}

I also have an ArrayList like this: ArrayList<A> listObj.

How can I check if that list contains an object using only some of the properties of A? E.g. considering only elementA for finding if object newA{elementA} is already in the list?

For object A I have defined an equals method, where I consider only the elementA, however this is not enough.