clearing or set null to objects in java

Question

I was recently looking into freeing up memory occupied by Java objects. While doing that I got confused about how objects are copied (shallow/deep) in Java and how to avoid

Answer 1

If you put the list into a hash map, the hash map now holds a reference to the list.

If you pass the list as an argument to a method, the method will have a reference to it for the duration of the method.

If you pass it to a thread to be manipulated, the thread will have a reference to the object until it terminates.

In all of these cases, if you set list = null, the references will still be maintained, but they will disappear after these references disappear.

If you simply clear the list, the references will still be valid, but will now point to a list that has suddenly been emptied, by means that may be unknown to the programmer and may be considered a bug, especially if you use the thread.