Question

I have two lists –

ArrayList<MyObject> list1 -> [obj1, obj2, obj3, obj4, obj5, obj6]

ArrayList<MyObject>  list2 -> [obj1, obj6, obj7, obj8]

Is there any utility method already existing in java api which can give a list of only common records of two?

expected list ->
[obj1, obj6]

MyObject looks like this –

class MyObject {
  public Integer number;
  public String name;
  public Integer parent;
  public String parentName;
}

I only need to use number and name to do the comparison.

---

i am aware of approach using retainAll or removeAll to get the desired list. The problem however is, I cannot override equals method of MyObject as it is used for some different purpose. And the retainAll or removeAll method doesn’t seems to accept Comparator object.

I know another solution is to iterate through the lists and find the common ones. I am looking if there is already some method which do it.

Thanks.

Answer 1

I don’t know of any cleaner way than what you already suggest.

However, if you need equality but can’t use equals (I’m not going to ask 😉 you could merge the lists and sort them, and then compare manually each element to the next, keeping only the duplicate ones.