Guava - How to remove from a list, based on a predicate, keeping track of what was removed?

Question

I have an ArrayList to be filtered, and various Guava Predicates to filter it with. This list will have only 50-100 elements.

I was planning on

Answer 1

I agree with Peter's anwser.

But if you want to have fun, you could also wrap each of your predicate inside a predicate which would delegate to the wrapped predicate, and store the values for which true is returned inside a Map> removedByPredicate :

class PredicateWrapper implements Predicate {
    private Predicate delegate;

    public PredicateWrapper(Predicate delegate) {
        this.delegate = delegate;
    }

    @Override
    public boolean apply(Foo foo) {
        boolean result = delegate.apply(foo);
        if (result) {
            List objectsRemoved = removedByPredicate.get(delegate);
            if (objectsRemoved == null) {
                objectsRemoved = Lists.newArrayList();
                removedByPredicate.put(delegate, objectsRemoved);
            }
            objectsRemoved.add(foo);
        }
        return result;
    }
}