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diff --git a/guava/src/com/google/common/collect/Interner.java b/guava/src/com/google/common/collect/Interner.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.Beta;
+
+/**
+ * Provides equivalent behavior to {@link String#intern} for other immutable
+ * types.
+ *
+ * @author Kevin Bourrillion
+ * @since 3.0
+ */
+@Beta
+public interface Interner<E> {
+  /**
+   * Chooses and returns the representative instance for any of a collection of
+   * instances that are equal to each other. If two {@linkplain Object#equals
+   * equal} inputs are given to this method, both calls will return the same
+   * instance.  That is, {@code intern(a).equals(a)} always holds, and {@code
+   * intern(a) == intern(b)} if and only if {@code a.equals(b)}. Note that
+   * {@code intern(a)} is permitted to return one instance now and a different
+   * instance later if the original interned instance was garbage-collected.
+   *
+   * <p><b>Warning:</b> do not use with mutable objects.
+   *
+   * @throws NullPointerException if {@code sample} is null
+   */
+  E intern(E sample);
+}