Initial Jack import.

Change-Id: I953cf0a520195a7187d791b2885848ad0d5a9b43

1 files changed, 76 insertions, 0 deletions

diff --git a/guava/src/com/google/common/collect/ForwardingObject.java b/guava/src/com/google/common/collect/ForwardingObject.java
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+/*
+ * Copyright (C) 2007 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.io.Serializable;
+
+/**
+ * An abstract base class for implementing the <a
+ * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
+ * The {@link #delegate()} method must be overridden to return the instance
+ * being decorated.
+ *
+ * <p>This class does <i>not</i> forward the {@code hashCode} and {@code equals}
+ * methods through to the backing object, but relies on {@code Object}'s
+ * implementation. This is necessary to preserve the symmetry of {@code equals}.
+ * Custom definitions of equality are usually based on an interface, such as
+ * {@code Set} or {@code List}, so that the implementation of {@code equals} can
+ * cast the object being tested for equality to the custom interface. {@code
+ * ForwardingObject} implements no such custom interfaces directly; they
+ * are implemented only in subclasses. Therefore, forwarding {@code equals}
+ * would break symmetry, as the forwarding object might consider itself equal to
+ * the object being tested, but the reverse could not be true. This behavior is
+ * consistent with the JDK's collection wrappers, such as
+ * {@link java.util.Collections#unmodifiableCollection}. Use an
+ * interface-specific subclass of {@code ForwardingObject}, such as {@link
+ * ForwardingList}, to preserve equality behavior, or override {@code equals}
+ * directly.
+ *
+ * <p>The {@code toString} method is forwarded to the delegate. Although this
+ * class does not implement {@link Serializable}, a serializable subclass may be
+ * created since this class has a parameter-less constructor.
+ *
+ * @author Mike Bostock
+ * @since 2.0 (imported from Google Collections Library)
+ */
+@GwtCompatible
+public abstract class ForwardingObject {
+
+  /** Constructor for use by subclasses. */
+  protected ForwardingObject() {}
+
+  /**
+   * Returns the backing delegate instance that methods are forwarded to.
+   * Abstract subclasses generally override this method with an abstract method
+   * that has a more specific return type, such as {@link
+   * ForwardingSet#delegate}. Concrete subclasses override this method to supply
+   * the instance being decorated.
+   */
+  protected abstract Object delegate();
+
+  /**
+   * Returns the string representation generated by the delegate's
+   * {@code toString} method.
+   */
+  @Override public String toString() {
+    return delegate().toString();
+  }
+
+  /* No equals or hashCode. See class comments for details. */
+}