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/*
* Copyright (c) 1997, 2023 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0, which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package com.sun.istack;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.lang.ref.WeakReference;
/**
* Pool of reusable objects that are indistinguishable from each other,
* such as JAXB marshallers.
*
* @author Kohsuke Kawaguchi
* @param type
*/
public interface Pool {
/**
* Gets a new object from the pool.
*
*
* If no object is available in the pool, this method creates a new one.
* @return an object from the pool
*/
@NotNull T take();
/**
* Returns an object back to the pool.
* @param t object to put back to pool
*/
void recycle(@NotNull T t);
/**
* Default implementation that uses {@link ConcurrentLinkedQueue}
* as the data store.
*
*
Note for Implementors
*
* Don't rely on the fact that this class extends from {@link ConcurrentLinkedQueue}.
* @param type
*/
abstract class Impl implements Pool {
private volatile WeakReference> queue;
/**
* Create new Impl
*/
protected Impl() {
}
/**
* Gets a new object from the pool.
*
*
* If no object is available in the pool, this method creates a new one.
*
* @return
* always non-null.
*/
@Override
public final @NotNull T take() {
T t = getQueue().poll();
if(t==null) {
return create();
}
return t;
}
/**
* Returns an object back to the pool.
* @param t object to put back to the pool
*/
@Override
public final void recycle(T t) {
getQueue().offer(t);
}
private ConcurrentLinkedQueue getQueue() {
WeakReference> q = queue;
if (q != null) {
ConcurrentLinkedQueue d = q.get();
if (d != null) {
return d;
}
}
// overwrite the queue
ConcurrentLinkedQueue d = new ConcurrentLinkedQueue<>();
queue = new WeakReference<>(d);
return d;
}
/**
* Creates a new instance of object.
*
*
* This method is used when someone wants to
* {@link #take() take} an object from an empty pool.
*
*
* Also note that multiple threads may call this method
* concurrently.
* @return an object from an empty pool
*/
protected abstract @NotNull T create();
}
}