Generic InternPool in Java?

Question

How would I write a generic InternPool in Java? Does it need a Internable interface?

String in Java has interning cap

Answer 1

I would separate the solution into two classes to have cleaner code and also this way getting rid of loop:

public class WeakPool {
    private final WeakHashMap> pool = new WeakHashMap>();
    public T get(T object) {
        final T res;
        WeakReference ref = pool.get(object);
        if (ref != null) {
            res = ref.get();
        } else {
            res = null;
        }
        return res;
    }
    public void put(T object) {
        pool.put(object, new WeakReference(object));
    }
}

and the interning class using the weak pool is very simple:

public class InternPool {

    private final WeakPool pool = new WeakPool();

    public synchronized T intern(T object) {
        T res = pool.get(object);
        if (res == null) {
            pool.put(object);
            res = object;
        }
        return res;
    }
}