ArrayList> - How to tidy up best?

Question

A quick question in between: I have a simple WeakRunnableList. Is this way ok to clean it up (removing dead references), or is there a more elegant and fast

Answer 1

Here is my take. WeakHashMap removes autmatically, so this should suffice. Beware of hashCode/equals semantics of Runnable though.

See also Are keySet entries of a WeakHashMap never null? WeakHashMap iteration and garbage collection

import java.util.WeakHashMap;

public class WeakRunnableList
{
    private WeakHashMap<Runnable, Void> _items = new WeakHashMap<Runnable, Void>();

    public void Add(Runnable r)
    {
        _items.put(r, null);
    }

    public void Execute()
    {
        Iterator<Runnable> iterator = _items.keySet().iterator();
        while (iterator.hasNext()) {
            Runnable runnable = iterator.next();
            if (runnable != null) {
                runnable.run();
                iterator.remove();
            }
        }
    }
}

Answer 2

You have a race condition between calls to item.get(). I would place item.get() into a local variable and use that.