Set.clear() and Set.addAll() vs Assignment which is better?

Question

Which of the following should be followed while setting Set elements and why?

private Set<TestDetailEntity> testDetails = new HashSet<>();

public void setTestDetails(Set<TestDetailEntity> testDetails) {
        this.testDetails.clear();
        this.testDetails.addAll(testDetails);
    }


public void setTestDetails(Set<TestDetailEntity> testDetails) {
        this.testDetails = testDetails;
    }

The first one iterates over the collection. What I am trying to ask here is which one is efficient way?

Well they do different things. One modifies an existing collection, with the parameter as an independent collection, whereas the other is just a straight assignment, copying the reference from the parameter to the field. — Jon Skeet, Aug 16 '16 at 05:34
I meant in terms of efficiency the first one iterates over the collection.Why Downvote? — Ganesh, Aug 16 '16 at 05:50
Downvoted because it's a very bad question - you've basically asked "Which is better, an apple or an orange?" You don't mention efficiency anywhere in the question, yet suddenly that's what you're asking about? — Jon Skeet, Aug 16 '16 at 05:54
Well I am new to stackoverflow. I might not have framed the question correctly you could have asked in comments. But downvoting is not the way to do it. — Ganesh, Aug 16 '16 at 05:55
If you're new to Stack Overflow, you may want to consider that you're not in the best position to tell others how they should behave on Stack Overflow. If you ask a bad question, you should expect it to be downvoted... that's the way SO works. You should probably read https://codeblog.jonskeet.uk/2010/08/29/writing-the-perfect-question/ — Jon Skeet, Aug 16 '16 at 05:56

score 2 · Answer 1 · answered Aug 16 '16 at 05:34

It completely depends on your goal.

The first takes a copy of the contents of the set.

The second keeps a reference to the set passed in, which is shared with the calling code.

Neither is preferred in the absense of more design constraints, although if setTestDetails is going to keep a reference to the passed-in set, that should be clearly documented. (Actually, it should be clearly documented either way.)

Set.clear() and Set.addAll() vs Assignment which is better?

1 Answers1