Question

final public class ImmutableWithObject {

    final Object obj;
    final List myList;

    ImmutableWithObject(Object obj1, List list)
    {
        this.obj = obj1;
        this.myList = ((List) ((ArrayList) list).clone());
    }

    public Object getObj() {
        return this.obj;
    }

    public List getMyList() {
        return (List) ((ArrayList<String>) this.myList).clone();
    }

    public static void main(String[] args) {

        ImmutableWithObject io = new ImmutableWithObject(new Date(), new ArrayList());

        ((Date) io.getObj()).setDate(22);

        System.out.println((Date) io.getObj());
    }
}

o/p : Mon Aug 22 00:50:04 IST 2011

which is incorrect.

Answer 1

You cannot make it immutable since this object cannot create copies of the contents of the list or the Object. Assuming that you mean to have getters for accessing those properties, the properties themselves were created elsewhere and can be changed in code external to this class that has a reference to it.

The only exception to this is if the contents of Object and List are themselves immutable. Then you can create an immutable copy of the list and you would be done.