Converting ArrayList to List ives NullPointerException

Question

Hello,
I have block of code.
    private ArrayList<SomeBean> list;
    private List<SomeBean> listNew;
    getter and setters
            for ( SomeBean itr : list ) {
               listNew.add(itr);
Gives me NullPointerException

Answer 1

You are not obliged to initialize it as List, it's just that you can't initialize with an abstract class. You have to use a class which is extended from the abstract class. Only such a class adds the needed information about the implementation, which the abstract class misses deliberately.
private List<SomeBean> listNew = new ArrayList<SomeBean>();
Now hte compiler knows which implementation of List you like to use.
If you return the list you return it as List<SomeBean>.
Timo