40

Possible Duplicate:
Is Java pass-by-reference?

Does a List object get passed by reference? In other words, if I pass an ArrayList (java.util.ArrayList) object to a class, will it be automatically updated when I change it?

Improve this question
2
  • 1
    Hint: ArrayList or List is not special in this regard. In fact no class is special in this regard. Commented Jul 9, 2012 at 14:25
  • 2
    All primitives and references are passed by value in Java. In your case you have a reference to a List (not a List as such) and the reference to it will be passed by value. Commented Jul 9, 2012 at 14:32

4 Answers 4

Reset to default
41

in other word: If I pass an ArrayList (java.util.ArrayList) object to a class, will it be automatically updated when I change it?

Yes

Does the List object passed by reference?

Value of reference would get passed

public updateList(List<String> names){
 //..
}

Explanation

When you call updateList(someOtherList); the value of someOtherList which is a reference will copied to names (another reference in method, bit by bit) so now both of them are referring to same instance in memory and thus it will change

See

Improve this answer
Sign up to request clarification or add additional context in comments.

Comments

20

Yes, a List that you pass to a method is passed by reference. Any objects you add to the List inside the method will still be in the List after the method returns.

Improve this answer

Comments

7

If you add to a list in one method, its original reference in first method will also contain the new item.

java is pass by value, and for objects this means the reference is passed by value.

Improve this answer

Comments

0

Yes, because You just pass a reference of ArrayList-Object, to your Object.

Improve this answer

Comments

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.