001/* 002 * Copyright (C) 2007 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 005 * in compliance with the License. You may obtain a copy of the License at 006 * 007 * http://www.apache.org/licenses/LICENSE-2.0 008 * 009 * Unless required by applicable law or agreed to in writing, software distributed under the License 010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 011 * or implied. See the License for the specific language governing permissions and limitations under 012 * the License. 013 */ 014 015package com.google.common.base; 016 017import com.google.common.annotations.GwtIncompatible; 018import java.lang.ref.ReferenceQueue; 019import java.lang.ref.SoftReference; 020import javax.annotation.CheckForNull; 021 022/** 023 * Soft reference with a {@code finalizeReferent()} method which a background thread invokes after 024 * the garbage collector reclaims the referent. This is a simpler alternative to using a {@link 025 * ReferenceQueue}. 026 * 027 * @author Bob Lee 028 * @since 2.0 029 */ 030@GwtIncompatible 031@ElementTypesAreNonnullByDefault 032public abstract class FinalizableSoftReference<T> extends SoftReference<T> 033 implements FinalizableReference { 034 /** 035 * Constructs a new finalizable soft reference. 036 * 037 * @param referent to softly reference 038 * @param queue that should finalize the referent 039 */ 040 protected FinalizableSoftReference(@CheckForNull T referent, FinalizableReferenceQueue queue) { 041 super(referent, queue.queue); 042 queue.cleanUp(); 043 } 044}