How do I copy the contents of one ArrayList into another?

Question

I have some data structures, and I would like to use one as a temporary, and another as not temporary.

ArrayList<Object> myObject = new ArrayList<Object>(); ArrayList<Object> myTempObject = new ArrayList<Object>();   //fill myTempObject here ....  //make myObject contain the same values as myTempObject myObject = myTempObject;  //free up memory by clearing myTempObject myTempObject.clear(); 

now the problem with this of course is that myObject is really just pointing to myTempObject, and so once myTempObject is cleared, so is myObject.

How do I retain the values from myTempObject in myObject using java?

Answer 1

You can use such trick:

myObject = new ArrayList<Object>(myTempObject); 

or use

myObject = (ArrayList<Object>)myTempObject.clone(); 

You can get some information about clone() method here

But you should remember, that all these ways will give you a copy of your List, not all of its elements. So if you change one of the elements in your copied List, it will also be changed in your original List.