/**
* Gets the next element in the iteration.
*
* @return the next element in the iteration.
* @throws java.util.NoSuchElementException if the iteration has exhausted all elements.
* @see java.util.Iterator#next()
* @see #hasNext()
*/
@Override
public T next() {
Assert.isTrue(hasNext(), new NoSuchElementException("The iteration has no more elements!"));
T value = iterators.peek().next();
nextCalled.set(true);
return value;
}
/**
* Constructs an instance of the BreadthFirstIterator class wrapping the Iterator of Iterators to
* collectively traverse the Iterators in order, left to right, top to bottom.
*
* @param iterators the Iterator of Iterators to encapsulate in a breadth-first traversal.
* @throws java.lang.NullPointerException if the Iterator of Iterators reference is null.
* @see java.util.Iterator
*/
public BreadthFirstIterator(final Iterator<Iterator<T>> iterators) {
Assert.notNull(iterators, "The Iterator of Iterators must not be null!");
for (Iterator<T> iterator : CollectionUtils.iterable(iterators)) {
if (iterator != null) {
this.iterators.add(iterator);
}
}
}
/**
* Determines whether another element is available in the iteration.
*
* @return a boolean value indicating whether another element is available in the iteration.
* @see java.util.Iterator#hasNext()
*/
@Override
public boolean hasNext() {
while (!(iterators.isEmpty() || iterators.peek().hasNext())) {
Assert.isFalse(
iterators.removeFirst().hasNext(),
new IllegalStateException("removing a non-empty Iterator"));
}
return (!iterators.isEmpty() && iterators.peek().hasNext());
}
/**
* Removes the current element in the iteration.
*
* @throws java.lang.IllegalStateException if the next method has not yet been called, or the
* remove method has already been called after the last call to the next method.
* @see java.util.Iterator#remove()
*/
@Override
public void remove() {
Assert.state(nextCalled.compareAndSet(true, false), "next was not called before remove");
iterators.peek().remove();
}
/**
* Constructs an instance of the {@link RegexFileFilter} class initialized with the given regular
* expression (regex), expressed as a {@link Pattern}.
*
* @param regularExpression regular expression (regex) used to match and filter {@link File}s.
* @throws IllegalArgumentException if the regular expression {@link Pattern} is null.
* @see java.util.regex.Pattern
*/
public RegexFileFilter(Pattern regularExpression) {
Assert.notNull(regularExpression, "The Regular Expression (Pattern) cannot be null");
this.regularExpression = regularExpression;
}