Initial Jack import.

Change-Id: I953cf0a520195a7187d791b2885848ad0d5a9b43

1 files changed, 80 insertions, 0 deletions

diff --git a/guava/src/com/google/common/collect/AbstractSequentialIterator.java b/guava/src/com/google/common/collect/AbstractSequentialIterator.java
new file mode 100644
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+++ b/guava/src/com/google/common/collect/AbstractSequentialIterator.java
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+/*
+ * Copyright (C) 2010 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 com.google.common.annotations.GwtCompatible;
+
+import java.util.NoSuchElementException;
+
+import javax.annotation.Nullable;
+
+/**
+ * This class provides a skeletal implementation of the {@code Iterator}
+ * interface for sequences whose next element can always be derived from the
+ * previous element. Null elements are not supported, nor is the
+ * {@link #remove()} method.
+ *
+ * <p>Example: <pre>   {@code
+ *
+ *   Iterator<Integer> powersOfTwo = 
+ *       new AbstractSequentialIterator<Integer>(1) {
+ *         protected Integer computeNext(Integer previous) {
+ *           return (previous == 1 << 30) ? null : previous * 2;
+ *         }
+ *       };}</pre>
+ *
+ * @author Chris Povirk
+ * @since 12.0 (in Guava as {@code AbstractLinkedIterator} since 8.0)
+ */
+@GwtCompatible
+public abstract class AbstractSequentialIterator<T>
+    extends UnmodifiableIterator<T> {
+  private T nextOrNull;
+
+  /**
+   * Creates a new iterator with the given first element, or, if {@code
+   * firstOrNull} is null, creates a new empty iterator.
+   */
+  protected AbstractSequentialIterator(@Nullable T firstOrNull) {
+    this.nextOrNull = firstOrNull;
+  }
+
+  /**
+   * Returns the element that follows {@code previous}, or returns {@code null}
+   * if no elements remain. This method is invoked during each call to
+   * {@link #next()} in order to compute the result of a <i>future</i> call to
+   * {@code next()}.
+   */
+  protected abstract T computeNext(T previous);
+
+  @Override
+  public final boolean hasNext() {
+    return nextOrNull != null;
+  }
+
+  @Override
+  public final T next() {
+    if (!hasNext()) {
+      throw new NoSuchElementException();
+    }
+    try {
+      return nextOrNull;
+    } finally {
+      nextOrNull = computeNext(nextOrNull);
+    }
+  }
+}