Java Programming

If I am using any unsynchronized class, how do I make sure I handle synchronization externally? Is this good enough:

public class Test{

    private ArrayList al = new ArrayList();

    private synchronized void add (T t){
        al.add(t);
    }

    private synchronized void remove (T t){
        al.remove(t);
    }
....
....
....
}

I will make sure any add/delete in other methods will call these two adder deleter methods. But correct me if was wrong, this way only ensure 2 threads are adding and 2 threads are deleting. It does not handle that 1 thread is adding, and at the same time, 1 thread is deleting. How do I handle that?

Thanks.