JAVA多线程并发——创建线程

第一章：线程的创建与实现

一、继承Thread类

代码示例：

public class ExtendThread {
    public static void main(String[] args) {
        Thread thread1 = new MyThread(1);
        Thread thread2 = new MyThread(2);
        thread1.start();
        thread2.start();
    }

    public static class MyThread extends Thread {

        int num;

        public MyThread(int num){
            this.num = num;
        }

        @Override
        public void run() {
            System.out.println("我是线程"+ num);
        }
    }
}

运行结果：

二、实现runnable接口

代码示例：

/**
 * 通过实现Runnable接口创建线程
 * 线程无返回值
 */
public class implementRunnable {
    public static void main(String[] args) throws InterruptedException {
        Runnable runnable1 = new MyRunnable(1);
        Runnable runnable2 = new MyRunnable(2);
        Thread thread1 = new Thread(runnable1);
        Thread thread2 = new Thread(runnable2);
        thread1.start();
        Thread.sleep(1000);
        thread2.start();
    }


    public static class MyRunnable implements Runnable {
        int num;

        public MyRunnable(int num) {
            this.num = num;
        }

        @Override
        public void run() {
            System.out.println("我是线程" + num);
        }
    }
}

运行结果：

三、简单匿名内部类写法

代码示例：

public class innerRunnable {

    public static void main(String[] args) {
        System.out.println("我是原线程");

        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("我是新线程");
            }
        });
        thread.start();
    }
}

运行结果：

四、实现Callable接口

该方式创建线程可以获取新线程的返回值，上面的方法均无返回值
示例代码：

/**
 * 通过实现Callable接口实现
 * 线程有返回值
 */
public class implementCallable {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        MyCallable myCallable1 = new MyCallable(1);
        FutureTask<String> futureTask1 = new FutureTask<>(myCallable1);
        Thread thread1 = new Thread(futureTask1);
        thread1.start();
        String str1 = futureTask1.get();
        System.out.println("线程返回值：" + str1);

        MyCallable myCallable2 = new MyCallable(2);
        FutureTask<String> futureTask2 = new FutureTask<>(myCallable2);
        Thread thread2 = new Thread(futureTask2);
        thread2.start();
        String str2 = futureTask2.get();
        System.out.println("线程返回值: " + str2);
    }

    public static class MyCallable implements Callable<String>{

        int num;

        public MyCallable(int num){
            this.num = num;
        }

        @Override
        public String call() throws Exception {
            System.out.println("新线程" + num + "开始执行");
            return "创建了线程" + num;
        }
    }
}

运行结果：

五、线程池

推荐使用最后一种，new ThreadPoolExecutor(int corePoolSize,
int maximumPoolSize,
long keepAliveTime,
TimeUnit unit,
BlockingQueue workQueue,
RejectedExecutionHandler handler) ;

/**
 * 通过Executor的几个默认的线程池配置
 */
public class ByExecutor {

    public static void main(String[] args) {
        //createCachedThreadPool();
        //createFixThreadPool();
        //createScheduledThreadPool();
        //createSingleThreadPool();
        createByThreadPoolExecutor();
    }

    /**
     * newCachedThreadPool
     * 核心线程数无限大
     * 会重复利用之前的线程
     * 没有旧线程会创建新线程
     */
    private static void createCachedThreadPool() {
        ExecutorService threadPool = Executors.newCachedThreadPool();
        while (true) {
            threadPool.execute(new Runnable() {
                @Override
                public void run() {
                    System.out.println("我是线程" + Thread.currentThread().getName());

                }
            });
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * newFixedThreadPool
     * 固定线程数
     * 当前没有可用线程则会等待
     * 不会创建新线程
     */
    private static void createFixThreadPool() {
        ExecutorService threadPool = Executors.newFixedThreadPool(3);
        while (true) {
            threadPool.execute(new Runnable() {
                @Override
                public void run() {
                    System.out.println("我是线程 " + Thread.currentThread());
                }
            });
        }
    }

    /**
     * newScheduledThreadPool
     * 支持延时执行
     * 固定线程数
     */
    private static void createScheduledThreadPool() {
        ScheduledExecutorService scheduledThreadPool = Executors.newScheduledThreadPool(2);
        long delay = 5;
        System.out.println(new Date().getSeconds());
        while (true) {
            scheduledThreadPool.schedule(new Runnable() {
                @Override
                public void run() {
                    System.out.println("我是定时线程：" + Thread.currentThread() + new Date().getSeconds());
                }
            }, delay, TimeUnit.SECONDS);
        }
    }

    /**
     * newSingleThreadPool
     * 单线程
     */
    private static void createSingleThreadPool() {
        ExecutorService threadPool = Executors.newSingleThreadExecutor();
        while (true) {
            threadPool.execute(new Runnable() {
                @Override
                public void run() {
                    System.out.println("我是single线程 " + Thread.currentThread());
                }
            });
        }
    }

    /**
     * 推荐的使用线程池的方式，通过构造方法创建
     */
    private static void createByThreadPoolExecutor() {
        ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(
                2,
                2,
                3,
                TimeUnit.SECONDS,
                new LinkedBlockingQueue<>(2),
                new ThreadPoolExecutor.CallerRunsPolicy());

        for (int i = 0; i < 10; i++) {
            //创建任务
            Runnable runnable = new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(20);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName());
                }
            };
            // 将任务交给线程池管理
            threadPoolExecutor.execute(runnable);
        }
    }
}