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 passed an ArrayList to a method then list = null will have no effect if there is a live reference to the list somewhere eg in the calling code. If you call list.clear() anywhere in the code the references to the objects from this list will be nulled. Passing a reference to a method is not shallow copying it is passing reference by-value