Java 线程池中线程池状态有哪些-java教程-PHP中文网

Java 线程池状态有哪些

java 线程池（threadpoolexecutor）内部使用一个原子整数 ctl 来同时存储线程池状态和线程数量。该整数的最高位用于表示状态，共有五种状态：running、shutdown、stop、tidying 和 terminated。这些状态决定了线程池对提交任务的处理方式以及工作线程的行为。

Java 线程池中线程池状态有哪些

从 RUNNING 到 SHUTDOWN 的触发条件是什么

当调用 shutdown() 方法时，线程池会从 RUNNING 状态转变为 SHUTDOWN 状态。在此状态下，线程池不再接受新任务，但会继续执行已提交队列中的任务。这是最平滑的关闭方式，允许正在运行的任务完成。

Java 线程池中线程池状态有哪些

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import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;

public class StateDemo {
    public static void main(String[] args) {
        ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newFixedThreadPool(2);
        System.out.println("Initial state: " + getStateName(executor));
        
        executor.submit(() -> System.out.println("Task running"));
        executor.shutdown();
        System.out.println("After shutdown: " + getStateName(executor));
    }

    private static String getStateName(ThreadPoolExecutor executor) {
        try {
            java.lang.reflect.Field ctlField = ThreadPoolExecutor.class.getDeclaredField("ctl");
            ctlField.setAccessible(true);
            long ctl = ctlField.getLong(executor);
            int runState = (int) (ctl & ~0x7fffffffL); // 提取高3位
            switch (runState) {
                case 0: return "RUNNING";
                case -536870912: return "SHUTDOWN";
                case -1073741824: return "STOP";
                case -1610612736: return "TIDYING";
                case -2147483648: return "TERMINATED";
                default: return "UNKNOWN";
            }
        } catch (Exception e) {
            return "ERROR";
        }
    }
}

从 SHUTDOWN 到 STOP 的触发条件是什么

当调用 shutdownNow() 方法时，线程池会直接从 RUNNING 或 SHUTDOWN 状态转变为 STOP 状态。在 STOP 状态下，线程池不再接受新任务，也不会处理队列中剩余的任务，并尝试中断所有正在执行的工作线程。如果线程池处于 SHUTDOWN 状态，调用 shutdownNow() 也会将其升级为 STOP 状态。

Java 线程池中线程池状态有哪些

import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.List;

public class StopDemo {
    public static void main(String[] args) throws InterruptedException {
        ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newFixedThreadPool(2);
        
        executor.submit(() -> {
            try { Thread.sleep(10000); } catch (InterruptedException e) {}
        });
        
        List<runnable> notExecuted = executor.shutdownNow();
        System.out.println("Not executed tasks: " + notExecuted.size());
        System.out.println("State after shutdownNow: " + getStateName(executor));
    }

    private static String getStateName(ThreadPoolExecutor executor) {
        try {
            java.lang.reflect.Field ctlField = ThreadPoolExecutor.class.getDeclaredField("ctl");
            ctlField.setAccessible(true);
            long ctl = ctlField.getLong(executor);
            int runState = (int) (ctl & ~0x7fffffffL);
            switch (runState) {
                case 0: return "RUNNING";
                case -536870912: return "SHUTDOWN";
                case -1073741824: return "STOP";
                case -1610612736: return "TIDYING";
                case -2147483648: return "TERMINATED";
                default: return "UNKNOWN";
            }
        } catch (Exception e) {
            return "ERROR";
        }
    }
}</runnable>