/*
* 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);
}