java异步&线程池

线程

1、继承Thread

	public static void main(String[] args){
    
    
		 System.out.println("main...start....");
		 Thread01 thread=new Thread01();
		 thread.start(); //启动线程
		 System.out.println("main...end....");
	}
	public static class Thread01 extends Thread {
    
    
	        @Override
	        public void run() {
    
    
	            System.out.println("当前线程：" + Thread.currentThread().getId());
	            int i = 10 / 2;
	            System.out.println("运行结果：" + i);
	        }
	}

2、实现Runable接口

	public static void main(String[] args){
    
    
		 System.out.println("main...start....");
		 Runable01 runable01 =new Runable01();
		 new Thread(runable01).start();	//启动线程
		 System.out.println("main...end....");
	}
	public static class Runable01 implements Runnable {
    
    
	        @Override
	        public void run() {
    
    
	            System.out.println("当前线程：" + Thread.currentThread().getId());
	            int i = 10 / 2;
	            System.out.println("运行结果：" + i);
	        }
	 }

3、实现Callable接口

	public static void main(String[] args){
    
    
		 System.out.println("main...start....");
		 FutureTask<Integer> futureTask = new FutureTask<>(new Callable01());
		 new Thread(futureTask).start();
		 //阻塞等待整个线程执行完成，获取返回结果
		 Integer integer = futureTask.get();
		 System.out.println("main...end...."+integer);
	}
	public static class Callable01 implements Callable<Integer> {
    
    
	        @Override
	        public Integer call() throws Exception {
    
    
	            System.out.println("当前线程：" + Thread.currentThread().getId());
	            int i = 10 / 2;
	            System.out.println("运行结果：" + i);
	            return i;
	        }
	}

4、线程池

4.1、简介

 	public static ExecutorService executor = Executors.newFixedThreadPool(10);
 
	public static void main(String[] args)  {
    
    
	        System.out.println("main...start....");
	        //以Runable为例
	        executor.execute(new Runable01());
		 	System.out.println("main...end....");
	}

	public static class Runable01 implements Runnable {
    
    
	        @Override
	        public void run() {
    
    
	            System.out.println("当前线程：" + Thread.currentThread().getId());
	            int i = 10 / 2;
	            System.out.println("运行结果：" + i);
	        }
	 }
 

4.2、创建线程池

	   	/**
         * 七大参数
         * 
         * corePoolSize：核心线程数[一直存在除非（allowCoreThreadTimeOut）]；线程池，创建好以后就准备就绪的线程数量，就等待来接收异步任务去执行
         *      5个  Thread thread=new Thread(); thread.start();
         * 
         * maximumPoolSize[200]：最大线程数量 控制资源
         * 
         * keepAliveTime；存活时间，如果当前正在运行的线程数量大于core数量
         *      释放空闲的线程（maximumPoolSize-corePoolSize），只要线程空闲大于指定的keepAliveTime
         * 
         * unit：时间单位
         * 
         * BlockingQueue<Runnable> workQueue:阻塞队列，如果任务有很多，就会将目前多的任务方队列里面
         *              只要有线程空闲，就回去队列里面取出新的任务继续执行
         * 
         * threadFactory：线程的创建工厂
         * 
         * handle：如果队列满了，按照我们指定的拒绝策略拒绝执行任务
         *
         * 工作顺序：
         * 1）、线程池创建，准备好core数量的核心线程，准备接受任务
         * 		1.1 core满了，就将再进来的任务放入阻塞队列中，空闲的core就会自己去阻塞队列获取任务执行
         * 		1.2 阻塞队列满了，就直接开新线程执行。最大只能开到max指定的数量
         * 		1.3 max满了就用RejectedExecutionHandler拒绝任务
         * 		1.4 max都执行完成，有很多空闲，在指定的时间以后keepAliveTime以后，释放max-core这些线程
         *
         *  new LinkedBlockingDeque<>() 默认是Integer的最大值，内存不够
         */
		ThreadPoolExecutor executor = new ThreadPoolExecutor(
						5,
		                200,
		                10,
		                TimeUnit.SECONDS,
		                new LinkedBlockingDeque<>(100000),
		                Executors.defaultThreadFactory(),
		                new ThreadPoolExecutor.AbortPolicy()
		);
        //Executors.newCachedThreadPool() core是0，所有都可回收
        //Executors.newFixedThreadPool() 固定大小，core=max；都不可回收
        //Executors.newScheduledThreadPool() 定时任务的线程池
        //Executors.newSingleThreadScheduledExecutor() 单线程的线程池，后台从队列里面获取任务，挨个执行

异步

1、runAsync

	public static ExecutorService executor = Executors.newFixedThreadPool(10);

    public static void main(String[] args) throws ExecutionException, InterruptedException {
    
    
        System.out.println("main...start....");

        CompletableFuture<Void> completableFuture = CompletableFuture.runAsync(() -> {
    
    
        
            System.out.println("当前线程：" + Thread.currentThread().getId());
            int i = 10 / 2;
            System.out.println("运行结果：" + i);
        }, executor);

		System.out.println("main...end....");
        
    }

2、supplyAsync

2.1、whenComplete（完成回调），exceptionally(异常感知)

	public static ExecutorService executor = Executors.newFixedThreadPool(10);

    public static void main(String[] args){
    
    
		System.out.println("main...start....");
   		/**
         * 方法完成后的感知
         */
        CompletableFuture<Integer> future = CompletableFuture.supplyAsync(() -> {
    
    
            System.out.println("当前线程：" + Thread.currentThread().getId());
            int i = 10 / 2;
            System.out.println("运行结果：" + i);
            return i;
        }, executor).whenComplete((res, exception) -> {
    
    
            //虽然能得到异常信息，但是没法修改返回数据
            System.out.println("异步任务成功完成了...结果是：" + res + "异常是：" + exception);
        }).exceptionally(throwable -> {
    
    
            //可以感知异常，同时返回默认值
            return 10;
        });
        Integer integer=future.get();
		System.out.println("main...end...."+integer);
 	}

2.2、handle（最终处理）

    public static void main(String[] args){
    
    
		System.out.println("main...start....");
       	/**
         * 方法执行完成后的处理
         */
        CompletableFuture<Integer> future = CompletableFuture.supplyAsync(() -> {
    
    
            System.out.println("当前线程：" + Thread.currentThread().getId());
            int i = 10 / 4;
            System.out.println("运行结果：" + i);
            return i;
        }, executor).handle((res, thr) -> {
    
    
            if (res != null) {
    
    
                return res * 2;
            }
            if (thr != null) {
    
    
                return 0;
            }
            return 0;
        });
        Integer integer=future.get();
		System.out.println("main...end...."+integer);
 	}

2.3、线程串行化

 		/**
         * 1）、thenRun：不能获取到上一步的执行结果，无返回值
         * .thenRunAsync(() -> {
         *             System.out.println("任务2启动了...");
         *         }, executor);
         * 2)、能接受上一步结果，但是无返回值
         *  .thenAcceptAsync(res -> {
         *             System.out.println("任务2启动了..." + res);
         *         }, executor);
         * 3)、thenApplyAsync：能接受上一步结果，有返回值
         */
       	CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
    
    
            System.out.println("当前线程：" + Thread.currentThread().getId());
            int i = 10 / 4;
            System.out.println("运行结果：" + i);
            return i;
        }, executor).thenApplyAsync(res -> {
    
    
            System.out.println("任务2启动了..." + res);
            return "Hello" + res;
        }, executor);

		System.out.println("main...end...."+future.get());

2.4、两任务组合——都完成

        CompletableFuture<Object> future01 = CompletableFuture.supplyAsync(() -> {
    
    
            System.out.println("任务1线程：" + Thread.currentThread().getId());
            int i = 10 / 4;
            System.out.println("任务1结束：" + i);
            return i;
        }, executor);

        CompletableFuture<Object> future02 = CompletableFuture.supplyAsync(() -> {
    
    
            System.out.println("任务2线程：" + Thread.currentThread().getId());
            System.out.println("任务2结束：");
            return "Hello";
        }, executor);

        future01.runAfterBothAsync(future02,()->{
    
    
            System.out.println("任务3开始...");
        },executor);

        future01.thenAcceptBothAsync(future02, (f1, f2) -> {
    
    
            System.out.println("任务3开始...之前的结果：" + f1 + "--->" + f2);
        }, executor);
        
        CompletableFuture<String> future = future01.thenCombineAsync(future02, (f1, f2) -> {
    
    
            return f1 + ":" + f2 + "-> Haha";
        }, executor);

2.5、两任务组合——一个完成

   		CompletableFuture<Object> future01 = CompletableFuture.supplyAsync(() -> {
    
    
            System.out.println("任务1线程：" + Thread.currentThread().getId());
            int i = 10 / 4;
            System.out.println("任务1结束：" + i);
            return i;
        }, executor);

        CompletableFuture<Object> future02 = CompletableFuture.supplyAsync(() -> {
    
    
            System.out.println("任务2线程：" + Thread.currentThread().getId());
            System.out.println("任务2结束：");
            return "Hello";
        }, executor);
   		/**
         * 两个任务，只要有一个完成，我们就执行任务3
         * runAfterEitherAsync：不感知结果，自己也无返回值
         * acceptEitherAsync：感知结果，自己没有返回值
         */
        future01.runAfterEitherAsync(future02, () -> {
    
    
            System.out.println("任务3开始...之前的结果：");
        }, executor);

        future01.acceptEitherAsync(future02,(res)->{
    
    
            System.out.println("任务3开始...之前的结果："+res);
        },executor);

        CompletableFuture<String> future = future01.applyToEitherAsync(future02, (res) -> {
    
    
            System.out.println("任务3开始...之前的结果：" + res);
            return res.toString() + "->哈哈";
        }, executor);

2.6、多任务组合

		CompletableFuture<String> future1= CompletableFuture.supplyAsync(() -> {
    
    
            System.out.println("任务1");
            return "任务1结果";
        },executor);

        CompletableFuture<String> future2 = CompletableFuture.supplyAsync(() -> {
    
    
            System.out.println("任务2");
            return "任务2结果";
        },executor);
        
        CompletableFuture<String> future3 = CompletableFuture.supplyAsync(() -> {
    
    
            System.out.println("任务3");
            return "任务3结果";
        },executor);

        CompletableFuture<Void> allOf = CompletableFuture.allOf(future1, future2 , future3 );
		allOf.get();	//等待所有结果完成
		
        CompletableFuture<Object> anyOf = CompletableFuture.anyOf(uture1, future2 , future3);
        anyOf.get();
        System.out.println("main...end..."+anyOf.get())