1 /* 2 * Copyright (C) 2007 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.collect; 18 19 import com.google.common.annotations.Beta; 20 21 /** 22 * Provides equivalent behavior to {@link String#intern} for other immutable 23 * types. 24 * 25 * @author Kevin Bourrillion 26 * @since 3.0 27 */ 28 @Beta 29 public interface Interner<E> { 30 /** 31 * Chooses and returns the representative instance for any of a collection of 32 * instances that are equal to each other. If two {@linkplain Object#equals 33 * equal} inputs are given to this method, both calls will return the same 34 * instance. That is, {@code intern(a).equals(a)} always holds, and {@code 35 * intern(a) == intern(b)} if and only if {@code a.equals(b)}. Note that 36 * {@code intern(a)} is permitted to return one instance now and a different 37 * instance later if the original interned instance was garbage-collected. 38 * 39 * <p><b>Warning:</b> do not use with mutable objects. 40 * 41 * @throws NullPointerException if {@code sample} is null 42 */ 43 E intern(E sample); 44 } 45
