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diff --git a/guava/src/com/google/common/collect/ImmutableEnumSet.java b/guava/src/com/google/common/collect/ImmutableEnumSet.java
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+++ b/guava/src/com/google/common/collect/ImmutableEnumSet.java
@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 2009 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;
+import java.util.Collection;
+import java.util.EnumSet;
+
+/**
+ * Implementation of {@link ImmutableSet} backed by a non-empty {@link
+ * java.util.EnumSet}.
+ *
+ * @author Jared Levy
+ */
+@GwtCompatible(serializable = true, emulated = true)
+@SuppressWarnings("serial") // we're overriding default serialization
+final class ImmutableEnumSet<E extends Enum<E>> extends ImmutableSet<E> {
+  /*
+   * Notes on EnumSet and <E extends Enum<E>>:
+   *
+   * This class isn't an arbitrary ForwardingImmutableSet because we need to
+   * know that calling {@code clone()} during deserialization will return an
+   * object that no one else has a reference to, allowing us to guarantee
+   * immutability. Hence, we support only {@link EnumSet}.
+   */
+  private final transient EnumSet<E> delegate;
+
+  ImmutableEnumSet(EnumSet<E> delegate) {
+    this.delegate = delegate;
+  }
+
+  @Override boolean isPartialView() {
+    return false;
+  }
+
+  @Override public UnmodifiableIterator<E> iterator() {
+    return Iterators.unmodifiableIterator(delegate.iterator());
+  }
+
+  @Override
+  public int size() {
+    return delegate.size();
+  }
+
+  @Override public boolean contains(Object object) {
+    return delegate.contains(object);
+  }
+
+  @Override public boolean containsAll(Collection<?> collection) {
+    return delegate.containsAll(collection);
+  }
+
+  @Override public boolean isEmpty() {
+    return delegate.isEmpty();
+  }
+
+  @Override public Object[] toArray() {
+    return delegate.toArray();
+  }
+
+  @Override public <T> T[] toArray(T[] array) {
+    return delegate.toArray(array);
+  }
+
+  @Override public boolean equals(Object object) {
+    return object == this || delegate.equals(object);
+  }
+
+  private transient int hashCode;
+
+  @Override public int hashCode() {
+    int result = hashCode;
+    return (result == 0) ? hashCode = delegate.hashCode() : result;
+  }
+
+  @Override public String toString() {
+    return delegate.toString();
+  }
+
+  // All callers of the constructor are restricted to <E extends Enum<E>>.
+  @Override Object writeReplace() {
+    return new EnumSerializedForm<E>(delegate);
+  }
+
+  /*
+   * This class is used to serialize ImmutableEnumSet instances.
+   */
+  private static class EnumSerializedForm<E extends Enum<E>>
+      implements Serializable {
+    final EnumSet<E> delegate;
+    EnumSerializedForm(EnumSet<E> delegate) {
+      this.delegate = delegate;
+    }
+    Object readResolve() {
+      // EJ2 #76: Write readObject() methods defensively.
+      return new ImmutableEnumSet<E>(delegate.clone());
+    }
+    private static final long serialVersionUID = 0;
+  }
+}