[I-tor-developer] Found/Resolved a bug in FilterIterator

[Thijs J. <ito...@th...>]

Dear all,

Erik and I discoverd a bug in the FilterIterator. It wasn't possible to 
iterate over a collection wit null elements. We've added a test to 
FilterIteratorTest to demonstrate the problem:

public void testIteratorWithNullValues(){
	Collection coll = Arrays.asList(new Object[]{null,null,null,"bla"});
	Iterator it = new FilterIterator(coll.iterator(), new AlwaysTruePredicate());
	assertTrue(it.hasNext());
	assertNull(it.next());
	assertNull(it.next());
	assertNull(it.next());
	assertEquals("bla",it.next());
	assertFalse(it.hasNext());
}

We solved the problem in the class IteratorAsStack which couldn't handle null 
elements. We added a new attribute topElementSet and changed the method 
isEmpty() and pop();

public class IteratorAsStack implements Stack {
	private Iterator delegate;
	private Object topElement;
	private boolean topElementSet=false;

	public IteratorAsStack(Iterator iterator) {
		this.delegate = iterator;
	}

	public Object peek() {
		if (isEmpty())
			throw new NoSuchElementException();
		return topElement;
	}

	public Object pop() {
		Object result = peek();
		topElementSet = false;
		return result;
	}

	public void push(Object object) {
		throw new UnsupportedOperationException();
	}

	public boolean isEmpty() {
		if (!topElementSet && delegate.hasNext()) {
			topElement = delegate.next();
			topElementSet = true;
		}
		return !topElementSet;
	}
}

The changes are committed to the cq2-itor branch.

Best regards,

Thijs
-- 
Thijs Janssen

th...@cq...
ito...@th...

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