Update #0 - First Release

sources/main/java/com/google/common/collect/PeekingIterator.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2008 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.common.collect;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+import com.google.common.annotations.GwtCompatible;
+
+/**
+ * An iterator that supports a one-element lookahead while iterating.
+ * 
+ * <p>
+ * See the Guava User Guide article on <a href=
+ * "http://code.google.com/p/guava-libraries/wiki/CollectionHelpersExplained#PeekingIterator">
+ * {@code PeekingIterator}</a>.
+ *
+ * @author Mick Killianey
+ * @since 2.0 (imported from Google Collections Library)
+ */
+@GwtCompatible
+public interface PeekingIterator<E> extends Iterator<E> {
+	/**
+	 * Returns the next element in the iteration, without advancing the iteration.
+	 *
+	 * <p>
+	 * Calls to {@code peek()} should not change the state of the iteration, except
+	 * that it <i>may</i> prevent removal of the most recent element via
+	 * {@link #remove()}.
+	 *
+	 * @throws NoSuchElementException if the iteration has no more elements
+	 *                                according to {@link #hasNext()}
+	 */
+	E peek();
+
+	/**
+	 * {@inheritDoc}
+	 *
+	 * <p>
+	 * The objects returned by consecutive calls to {@link #peek()} then
+	 * {@link #next()} are guaranteed to be equal to each other.
+	 */
+	@Override
+	E next();
+
+	/**
+	 * {@inheritDoc}
+	 *
+	 * <p>
+	 * Implementations may or may not support removal when a call to {@link #peek()}
+	 * has occurred since the most recent call to {@link #next()}.
+	 *
+	 * @throws IllegalStateException if there has been a call to {@link #peek()}
+	 *                               since the most recent call to {@link #next()}
+	 *                               and this implementation does not support this
+	 *                               sequence of calls (optional)
+	 */
+	@Override
+	void remove();
+}