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内置线程池的核心参数分析配置

news 2025/10/22 8:42:01

ThreadPoolExecutor关键字包括五个参数 corePoolSize、maximumPool、keepAliveTime、unit、workQueue

corePoolSize表示核心进程数, maximumPool表示最大线程数、workQueue表示阻塞队列中进程数

用一个通俗易懂的例子来理解，core这个核心进程数相当于银行工作窗口，workqueue在排队办理业务的人、max表示能开启总共的总窗口。

core设为5，max设为10（其中包括core的5个剩余的是临时的），workqueue设为20则

情况1 来了20个人会直接去排队其中的5个人等着核心core处理

情况2 来了25个人 5个人去core办理剩余20个人把排队的位子坐满

情况3 来了26个人前25个人和情况2类似最后到的1个人直接到临时窗口办理业务

情况4 来了30个人其中25个人情况处理和情况2类似剩余的5个人会直接把剩余的5个临时窗口站全了

情况5 来了31个人那么前三十个人和情况三类似舍弃最后一个人（线程池的执行策略：拒绝执行）

补充：临时窗口啥时候关闭呢？当所有的窗口都空闲时，并且空闲的时间超过keepAliveTime，那么5个临时窗口会全部关闭，5个core核心窗口保持打开。

代码示例：

public class ThreadPool {//工作进程列表private List<WorkThread> workList = new ArrayList<>();//任务线程private List<Runnable> runnableList = new ArrayList<>();private int coreSize;private int maxSize;private int queueSize;public ThreadPool(int coreSize,int maxSize,int queueSize){this.coreSize = coreSize;this.maxSize = maxSize;this.queueSize = queueSize;//启动任务for(int i = 0; i < coreSize; i++){WorkThread work = new WorkThread(runnableList);new Thread(work).start();workList.add(work);}}public void add(Runnable runnable){synchronized (runnableList){if(runnableList.size() < queueSize){ //核心进程工作//添加并唤醒runnableList.add(runnable);runnableList.notify();}else if(workList.size() < maxSize){ //临时进程工作System.out.println("临时进程启用");WorkThread work = new WorkThread(runnableList);new Thread(work).start();workList.add(work);//让创建的临时进程处理任务runnableList.add(runnable);runnableList.notify();}else{System.out.println("拒绝执行");}}}
}

public class WorkThread implements Runnable{private List<Runnable> runnableList;public WorkThread(List<Runnable> runnableList){this.runnableList = runnableList;}public void run(){Runnable runnable = null;while(true){synchronized (runnableList) {//判断是否为空while (runnableList.isEmpty()) {//执行等待try {runnableList.wait();} catch (InterruptedException e) {throw new RuntimeException(e);}}//不空继续执行 取出进程runnable = runnableList.remove(0);}//执行进程代码runnable.run();}}
}

public class Test {public static void main(String[] args){//传值ThreadPool pool = new ThreadPool(5,10,20);for(int i = 0; i < 20; i++){pool.add(new TestWork(i));}}//自定义任务类static class TestWork implements Runnable{private int count;public TestWork(int count){this.count = count;}public void run(){//延时try {Thread.sleep(2000);} catch (InterruptedException e) {throw new RuntimeException(e);}System.out.println(Thread.currentThread().getName() + "执行进程: " + count);}}
}

可以调整任务数来观察结果，会完全符合上述的运行逻辑

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