技術標籤：多執行緒

首先建立一個 Runnable 介面的實現類（當然也可以是 Callable 介面，我們上面也說了兩者的區別。）

MyRunnable.java

import java.util.Date;

/**
 * 這是一個簡單的Runnable類，需要大約5秒鐘來執行其任務。
 * @author shuang.kou
 */
public class MyRunnable implements Runnable {

    private String command;

    public MyRunnable(String s) {
        this.command =
 
 s;
    }

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName() + " Start. Time = " + new Date());
        processCommand();
        System.out.println(Thread.currentThread().getName() + " End. Time = " + new Date());
    }

    private
 
 void processCommand() {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    @Override
    public String toString() {
        return this.command;
    }
}

編寫測試程式，我們這裡以阿里巴巴推薦的使用 ThreadPoolExecutor 建構函式自定義引數的方式來建立執行緒池。

ThreadPoolExecutorDemo.java

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class ThreadPoolExecutorDemo {

    private static final int CORE_POOL_SIZE = 5;
    private static final int MAX_POOL_SIZE = 10;
    private static final int QUEUE_CAPACITY = 100;
    private static final Long KEEP_ALIVE_TIME = 1L;
    public static void main(String[] args) {

        //使用阿里巴巴推薦的建立執行緒池的方式
        //通過ThreadPoolExecutor建構函式自定義引數建立
        ThreadPoolExecutor executor = new ThreadPoolExecutor(
                CORE_POOL_SIZE,
                MAX_POOL_SIZE,
                KEEP_ALIVE_TIME,
                TimeUnit.SECONDS,
                new ArrayBlockingQueue<>(QUEUE_CAPACITY),
                new ThreadPoolExecutor.CallerRunsPolicy());

        for (int i = 0; i < 10; i++) {
            //建立WorkerThread物件（WorkerThread類實現了Runnable 介面）
            Runnable worker = new MyRunnable("" + i);
            //執行Runnable
            executor.execute(worker);
        }
        //終止執行緒池
        executor.shutdown();
        while (!executor.isTerminated()) {
        }
        System.out.println("Finished all threads");
    }
}

可以看到我們上面的程式碼指定了：

1,corePoolSize: 核心執行緒數為 5。
2,maximumPoolSize ：最大執行緒數 10
3,keepAliveTime : 等待時間為 1L。
4,unit: 等待時間的單位為 TimeUnit.SECONDS。
5,workQueue：任務佇列為 ArrayBlockingQueue，並且容量為 100;
6,handler:飽和策略為 CallerRunsPolicy。

Output：

pool-1-thread-3 Start. Time = Sun Apr 12 11:14:37 CST 2020
pool-1-thread-5 Start. Time = Sun Apr 12 11:14:37 CST 2020
pool-1-thread-2 Start. Time = Sun Apr 12 11:14:37 CST 2020
pool-1-thread-1 Start. Time = Sun Apr 12 11:14:37 CST 2020
pool-1-thread-4 Start. Time = Sun Apr 12 11:14:37 CST 2020
pool-1-thread-3 End. Time = Sun Apr 12 11:14:42 CST 2020
pool-1-thread-4 End. Time = Sun Apr 12 11:14:42 CST 2020
pool-1-thread-1 End. Time = Sun Apr 12 11:14:42 CST 2020
pool-1-thread-5 End. Time = Sun Apr 12 11:14:42 CST 2020
pool-1-thread-1 Start. Time = Sun Apr 12 11:14:42 CST 2020
pool-1-thread-2 End. Time = Sun Apr 12 11:14:42 CST 2020
pool-1-thread-5 Start. Time = Sun Apr 12 11:14:42 CST 2020
pool-1-thread-4 Start. Time = Sun Apr 12 11:14:42 CST 2020
pool-1-thread-3 Start. Time = Sun Apr 12 11:14:42 CST 2020
pool-1-thread-2 Start. Time = Sun Apr 12 11:14:42 CST 2020
pool-1-thread-1 End. Time = Sun Apr 12 11:14:47 CST 2020
pool-1-thread-4 End. Time = Sun Apr 12 11:14:47 CST 2020
pool-1-thread-5 End. Time = Sun Apr 12 11:14:47 CST 2020
pool-1-thread-3 End. Time = Sun Apr 12 11:14:47 CST 2020
pool-1-thread-2 End. Time = Sun Apr 12 11:14:47 CST 2020