jdk8-mips64-public/jaxws: src/share/jaxws_classes/com/sun/istack/internal/Pool.java@9c07ef4934dd

     1 /*

     2  * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    26 package com.sun.istack.internal;

    28 import java.util.concurrent.ConcurrentLinkedQueue;

    29 import java.lang.ref.WeakReference;

    31 /**

    32  * Pool of reusable objects that are indistinguishable from each other,

    33  * such as JAXB marshallers.

    34  *

    35  * @author Kohsuke Kawaguchi

    36  */

    37 public interface Pool<T> {

    39     /**

    40      * Gets a new object from the pool.

    41      *

    42      * <p>

    43      * If no object is available in the pool, this method creates a new one.

    44      */

    45     @NotNull T take();

    47     /**

    48      * Returns an object back to the pool.

    49      */

    50     void recycle(@NotNull T t);

    52     /**

    53      * Default implementation that uses {@link ConcurrentLinkedQueue}

    54      * as the data store.

    55      *

    56      * <h2>Note for Implementors</h2>

    57      * <p>

    58      * Don't rely on the fact that this class extends from {@link ConcurrentLinkedQueue}.

    59      */

    60     public abstract class Impl<T> implements Pool<T> {

    62         private volatile WeakReference<ConcurrentLinkedQueue<T>> queue;

    64         /**

    65          * Gets a new object from the pool.

    66          *

    67          * <p>

    68          * If no object is available in the pool, this method creates a new one.

    69          *

    70          * @return

    71          *      always non-null.

    72          */

    73         public final @NotNull T take() {

    74             T t = getQueue().poll();

    75             if(t==null) {

    76                 return create();

    77             }

    78             return t;

    79         }

    81         /**

    82          * Returns an object back to the pool.

    83          */

    84         public final void recycle(T t) {

    85             getQueue().offer(t);

    86         }

    88         private ConcurrentLinkedQueue<T> getQueue() {

    89             WeakReference<ConcurrentLinkedQueue<T>> q = queue;

    90             if (q != null) {

    91                 ConcurrentLinkedQueue<T> d = q.get();

    92                 if (d != null) {

    93                     return d;

    94                 }

    95             }

    96             // overwrite the queue

    97             ConcurrentLinkedQueue<T> d = new ConcurrentLinkedQueue<T>();

    98             queue = new WeakReference<ConcurrentLinkedQueue<T>>(d);

   100             return d;

   101         }

   103         /**

   104          * Creates a new instance of object.

   105          *

   106          * <p>

   107          * This method is used when someone wants to

   108          * {@link #take() take} an object from an empty pool.

   109          *

   110          * <p>

   111          * Also note that multiple threads may call this method

   112          * concurrently.

   113          */

   114         protected abstract @NotNull T create();

   115     }

   116 }

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