java.util.concurrent
包下的 ThreadPoolExecutor
和 ScheduledThreadPoolExecutor
类。你可以在GitHub上查看和下载OpenJDK项目的源代码:https://github.com/openjdk
Java线程池的源码涉及到很多类和方法,这里给出一个简化版的线程池实现,仅供参考。
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;
public class SimpleThreadPool {
private final AtomicInteger ctl = new AtomicInteger(0);
private static final int COUNT_BITS = Integer.SIZE 3;
private static final int CAPACITY = (1 << COUNT_BITS) 1;
private static final int RUNNING = 1 << COUNT_BITS;
private static final int SHUTDOWN = 0 << COUNT_BITS;
private static final int STOP = 1 << COUNT_BITS;
private static final int TIDYING = 2 << COUNT_BITS;
private static final int TERMINATED = 3 << COUNT_BITS;
private final BlockingQueue<Runnable> workQueue;
private final ThreadFactory threadFactory;
private final RejectedExecutionHandler handler;
private final Worker[] workers;
private int corePoolSize;
private int maximumPoolSize;
private long keepAliveTime;
private boolean allowCoreThreadTimeOut;
public SimpleThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) {
this.corePoolSize = corePoolSize;
this.maximumPoolSize = maximumPoolSize;
this.keepAliveTime = unit.toNanos(keepAliveTime);
this.workQueue = workQueue;
this.threadFactory = threadFactory;
this.handler = handler;
this.workers = new Worker[corePoolSize];
}
public void execute(Runnable command) {
// ...省略部分代码...
}
private void addWorker(Runnable firstTask) {
// ...省略部分代码...
}
private void ensurePrestart() {
// ...省略部分代码...
}
private boolean isRunning(int c) {
return c < 0 && c != SHUTDOWN;
}
private boolean compareAndIncrementWorkerCount(int expect) {
return ctl.compareAndSet(expect, expect + 1);
}
private boolean compareAndDecrementWorkerCount(int expect) {
return ctl.compareAndSet(expect, expect 1);
}
private void tryTerminate() {
// ...省略部分代码...
}
private void processWorkerExit(Worker w, boolean completedAbruptly) {
// ...省略部分代码...
}
private void runWorker(Worker w) {
// ...省略部分代码...
}
final void runTask(Runnable task) {
// ...省略部分代码...
}
final void reject(Runnable command) {
handler.rejectedExecution(command, this);
}
static class Worker extends Thread {
// ...省略部分代码...
}
}
这个简化版的线程池实现了基本的线程池功能,包括提交任务、创建工作线程、回收工作线程等,为了简洁起见,省略了很多细节和错误处理,在实际使用中,建议使用Java标准库提供的java.util.concurrent.ThreadPoolExecutor
类,它提供了更完善的线程池实现。
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