In the Java collections (array, LinkedList, Set), when an object is added, does it saves a copy of the reference or copy the entire object to the collection. And if I change the original object does it effect the collection's object?

CodePudding user response：

In the java collections (Array , LinkedList , Set) when an object is added does it saves a copy of the reference or copy the entire object to the collection.

It saves a reference. It does not copy the object.

This can be inferred from the javadoc for the Collection.add method:

boolean add(E e)

Ensures that this collection contains the specified element. Returns true if this collection changed as a result of the call.

Notice that it says that the collection will contain the specified element ... not a copy of the specified element.

If i change the original object does it effect the collection's object?

Yes. They are the same object.

CodePudding user response：

Yes, if you change the original object it does change the object inside the Collection.

You can read a similar question here which talks about java being a pass by reference: Is Java "pass-by-reference" or "pass-by-value"?