com.sun.util.reentrant.ReentrantContextProviderCLQ Maven / Gradle / Ivy
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package com.sun.util.reentrant;
import java.lang.ref.Reference;
import java.util.concurrent.ConcurrentLinkedQueue;
/**
* This ReentrantContextProvider implementation uses one ConcurrentLinkedQueue
* to store all ReentrantContext instances (thread and its child contexts)
*
* Note: this implementation keeps less contexts in memory depending on the
* concurrent active threads in contrary to a ThreadLocal provider. However,
* it is slower in highly concurrent workloads.
*
* @param ReentrantContext subclass
*/
public abstract class ReentrantContextProviderCLQ
extends ReentrantContextProvider
{
// ReentrantContext queue to store all contexts
private final ConcurrentLinkedQueue> ctxQueue
= new ConcurrentLinkedQueue>();
/**
* Create a new ReentrantContext provider using the given reference type
* among hard, soft or weak based using a ConcurrentLinkedQueue storage
*
* @param refType reference type
*/
public ReentrantContextProviderCLQ(final int refType) {
super(refType);
}
/**
* Give a ReentrantContext instance for the current thread
*
* @return ReentrantContext instance
*/
@Override
public final K acquire() {
K ctx = null;
// Drain queue if all referent are null:
Reference ref = null;
while ((ctx == null) && ((ref = ctxQueue.poll()) != null)) {
ctx = ref.get();
}
if (ctx == null) {
// create a new ReentrantContext if none is available
ctx = newContext();
ctx.usage = USAGE_CLQ;
}
return ctx;
}
/**
* Restore the given ReentrantContext instance for reuse
*
* @param ctx ReentrantContext instance
*/
@Override
public final void release(final K ctx) {
if (ctx.usage == USAGE_CLQ) {
ctxQueue.offer(getOrCreateReference(ctx));
}
}
}