Author: david.lloyd(a)jboss.com Date: 2008-07-28 17:11:10 -0400 (Mon, 28 Jul 2008) New Revision: 4433 Modified: remoting3/trunk/util/src/main/java/org/jboss/cx/remoting/util/CollectionUtil.java Log: Add iterator/iterable combining methods. Modified: remoting3/trunk/util/src/main/java/org/jboss/cx/remoting/util/CollectionUtil.java =================================================================== --- remoting3/trunk/util/src/main/java/org/jboss/cx/remoting/util/CollectionUtil.java 2008-07-26 20:09:43 UTC (rev 4432) +++ remoting3/trunk/util/src/main/java/org/jboss/cx/remoting/util/CollectionUtil.java 2008-07-28 21:11:10 UTC (rev 4433) @@ -451,6 +451,14 @@ return unroll(iterator, type, 0); } + /** + * Convert an iterator to an array in reverse order. The iterator should be relatively short to avoid blowing out the + * stack. + * + * @param iterator the iterator + * @param type the array element type + * @return the array + */ public static <T> T[] toArrayReversed(final Iterator<? extends T> iterator, final Class<T> type) { return unrollReversed(iterator, type, 0); } @@ -648,4 +656,117 @@ original.previous(); } } + + /** + * Combine two {@code Iterator}s into one. + * + * @param first the first {@code Iterator} + * @param second the second {@code Iterator} + * @return a combined {@code Iterator} + */ + public static <T> Iterator<T> combine(final Iterator<? extends T> first, final Iterator<? extends T> second) { + if (first == null) { + throw new NullPointerException("first is null"); + } + if (second == null) { + throw new NullPointerException("second is null"); + } + return new Iterator<T>() { + private Iterator<? extends T> current = first; + private Iterator<? extends T> next = second; + + public boolean hasNext() { + if (current == null) { + return false; + } + if (! current.hasNext()) { + current = next; + next = null; + } + return current != null && current.hasNext(); + } + + public T next() { + if (current == null) { + throw new NoSuchElementException("next() past end of iterator"); + } + return current.next(); + } + + public void remove() { + current.remove(); + } + }; + } + + /** + * Combine three {@code Iterator}s into one. + * + * @param first the first {@code Iterator} + * @param second the second {@code Iterator} + * @param third the third {@code Iterator} + * @return a new combined {@code Iterator} + */ + public static <T> Iterator<T> combine(final Iterator<? extends T> first, final Iterator<? extends T> second, final Iterator<? extends T> third) { + return combine(combine(first, second), third); + } + + /** + * Combine four {@code Iterator}s into one. + * + * @param first the first {@code Iterator} + * @param second the second {@code Iterator} + * @param third the third {@code Iterator} + * @param fourth the fourth {@code Iterator} + * @return a new combined {@code Iterator} + */ + public static <T> Iterator<T> combine(final Iterator<? extends T> first, final Iterator<? extends T> second, final Iterator<? extends T> third, final Iterator<? extends T> fourth) { + return combine(combine(first, second), combine(third, fourth)); + } + + /** + * Combine two {@code Iterable}s into one. + * + * @param first the first {@code Iterable} + * @param second the second {@code Iterable} + * @return a new combined {@code Iterable} + */ + public static <T> Iterable<T> combine(final Iterable<? extends T> first, final Iterable<? extends T> second) { + if (first == null) { + throw new NullPointerException("first is null"); + } + if (second == null) { + throw new NullPointerException("second is null"); + } + return new Iterable<T>() { + public Iterator<T> iterator() { + return combine(first.iterator(), second.iterator()); + } + }; + } + + /** + * Combine three {@code Iterable}s into one. + * + * @param first the first {@code Iterable} + * @param second the second {@code Iterable} + * @param third the third {@code Iterable} + * @return a new combined {@code Iterable} + */ + public static <T> Iterable<T> combine(final Iterable<? extends T> first, final Iterable<? extends T> second, final Iterable<? extends T> third) { + return combine(combine(first, second), third); + } + + /** + * Combine four {@code Iterable}s into one. + * + * @param first the first {@code Iterable} + * @param second the second {@code Iterable} + * @param third the third {@code Iterable} + * @param fourth the fourth {@code Iterable} + * @return a new combined {@code Iterable} + */ + public static <T> Iterable<T> combine(final Iterable<? extends T> first, final Iterable<? extends T> second, final Iterable<? extends T> third, final Iterable<? extends T> fourth) { + return combine(combine(first, second), combine(third, fourth)); + } }