java线程池导出线程 java线程池execute方法

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footballboy 2023-12-10 07:29:01

文章标签 java线程池导出线程 thread 多进程并发编程多线程 文章分类 Java 后端开发

线程的两种执行方式：

1.execute()执行:

(new Runnable)无返回值的:

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


public class ThreadDemo58 {
    public static void main(String[] args) {

        // 创建线程池
        ThreadPoolExecutor executor = new ThreadPoolExecutor(
                5, 5,
                0, TimeUnit.SECONDS,
                new LinkedBlockingQueue<>(5));
        for (int i = 0; i < 11; i++) {
            int finalI = i;
            executor.execute(new Runnable() {
                @Override
                public void run() {
                    System.out.println("任务：" + finalI + "，线程名：" +
                            Thread.currentThread().getName());
                }
            });
        }
    }
}

2.submit()执行:

(new Runnable无返回值/new Callable有返回值的>

import java.util.Random;
import java.util.concurrent.*;

public class ThreadPoolDemo61 {
    public static void main(String[] args) throws ExecutionException, InterruptedException {

        ThreadPoolExecutor executor = new ThreadPoolExecutor(
                5, 5, 0, TimeUnit.SECONDS,
                new LinkedBlockingQueue<>(1000)
        );
        // 返回返回值
        Future<Integer> future = executor.submit(new Callable<Integer>() {
            @Override
            public Integer call() throws Exception {
                int num = new Random().nextInt(10);
                System.out.println("线程池生成了随机数：" + num);
                return num;
            }
        });
        System.out.println("main 得到返回值：" + future.get());
    }
}

两者区别：

execute只能执行Runnable 任务，它是无返回值的; submit 它既能执行Runnable无返回值的任务，也能执行Callable有返回值的任务。
execute执行任务如果有OM异常会将异常打印到控制台; 而submit执行任务出现了OM异常时不会打印异常。

线程池的两种关闭方式：

线程池的特征:线程池相比于线程来说是长生命周期，即使没有任务了，也会运行并等待任务。

1.shutdown():

import java.util.Random;
import java.util.concurrent.*;

public class ThreadDemo62 {
    public static void main(String[] args) throws ExecutionException, InterruptedException {

        ThreadPoolExecutor executor = new ThreadPoolExecutor(
                5, 5, 0, TimeUnit.SECONDS,
                new LinkedBlockingQueue<>(1000)
        );
        // 返回返回值
        Future<Integer> future = executor.submit(new Callable<Integer>() {
            @Override
            public Integer call() throws Exception {
                int num = new Random().nextInt(10);
                System.out.println("线程池生成了随机数：" + num);
                return num;
            }
        });
        System.out.println("main 得到返回值：" + future.get());
        // 关闭线程池
        executor.shutdown();
    }
}

1.shutdownNow():

import java.util.Random;
import java.util.concurrent.*;

public class ThreadDemo62 {
    public static void main(String[] args) throws ExecutionException, InterruptedException {

        ThreadPoolExecutor executor = new ThreadPoolExecutor(
                5, 5, 0, TimeUnit.SECONDS,
                new LinkedBlockingQueue<>(1000)
        );
        // 返回返回值
        Future<Integer> future = executor.submit(new Callable<Integer>() {
            @Override
            public Integer call() throws Exception {
                int num = new Random().nextInt(10);
                System.out.println("线程池生成了随机数：" + num);
                return num;
            }
        });
        System.out.println("main 得到返回值：" + future.get());
        // 关闭线程池
        executor.shutdownNow();
    }
}

两者区别：

（执行复杂任务时会体现出区别）

shutdown():拒绝新任务加入，等待线程池中的任务队列执行完之后，再停止线程池。最后清空线程池中的线程。
shutdownNow() :拒绝执行新任务，不会等待任务队列中的任务执行完成，就停止线程池。最后清空线程池中的线程。

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

public class ThreadDemo63 {
    public static void main(String[] args) {
        ThreadPoolExecutor executor = new ThreadPoolExecutor(
                10, 10, 0, TimeUnit.SECONDS,
                new LinkedBlockingQueue<>(1000)
        );
        for (int i = 0; i < 100; i++) {
            int finalI = i;
            executor.submit(new Runnable() {
                @Override
                public void run() {
                    System.out.println(String.format("编号：%d，线程名：%s",
                            finalI, Thread.currentThread().getName()));
                }
            });
        }
        // 正常关闭
        executor.shutdown();
//        executor.shutdownNow();


    }
}