java | 单线程线程池

newSingleThreadExecutor

public static ExecutorService newSingleThreadExecutor() {
        return new FinalizableDelegatedExecutorService
            (new ThreadPoolExecutor(1, 1,
                                    0L, TimeUnit.MILLISECONDS,
                                    new LinkedBlockingQueue<Runnable>()));
    }

使用场景

• 希望多个任务排队执行，线程固定为 1，任务多于 1 时，会放入无界队列排队，执行完毕后，这唯一线程也不会被释放

区别

• 自己创建一个单线程串行执行任务，如果任务执行失败而终止那么，没有任何补救措施，而线程池还会创建一个新的线程，保证池的正常工作
• Executors.newSingleThreadExecutor() 线程个数始终为 1，不能修改
  • FinalizableDelegatedExecutorService 应用的是装饰器模式，只能对外暴露 ExecutorService 接口，因此不能调用 ThreadPoolExecutor 中特有方法
• Executors.newFixedThreadPool(1) 初始为 1，以后还可以修改
  • 对外暴露的是 ThreadPoolExecutor 对象，可以强转后调用 setCorePoolSize 等方法进行修改

package com.redisc;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

@Slf4j(topic = "c.Test")
public class Run {

    public static void main(String[] args) throws InterruptedException {
        ExecutorService pool = Executors.newSingleThreadExecutor();
        pool.execute(() -> {
            log.debug("1");
            int i = 1 / 0;
        });

        pool.execute(() -> {
            log.debug("2");
        });

        pool.execute(() -> {
            log.debug("3");
        });

    }
}

输出

23:49:58.157 [pool-1-thread-1] DEBUG c.Test - 1
23:49:58.160 [pool-1-thread-2] DEBUG c.Test - 2
23:49:58.160 [pool-1-thread-2] DEBUG c.Test - 3
Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero
	at com.redisc.Run.lambda$main$0(Run.java:16)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)