线程池的使用

1. 三大方法

建立单个线程的线程池

public class juc_pooldemo {
    public static void main(String[] args) {
         ExecutorService pool = Executors.newSingleThreadExecutor();  //单个线程的线程池
        try {
            for (int i = 0; i < 10; i++) {
                pool.execute(() -> {  //lanmbda表达式创建线程，并执行线程
                    System.out.println(Thread.currentThread().getName());
                    System.out.println(Runtime.getRuntime().availableProcessors());  //获得cpu核数
                });
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            pool.shutdown();  //关闭线程池
        }
    }
}

建立固定线程数的线程池

public class juc_pooldemo {
    public static void main(String[] args) {
        ExecutorService pool = Executors.newFixedThreadPool(5);  //固定数量的线程池
        try {
            for (int i = 0; i < 10; i++) {
                pool.execute(() -> {  //lanmbda表达式创建线程，并执行线程
                    System.out.println(Thread.currentThread().getName());
                    System.out.println(Runtime.getRuntime().availableProcessors());  //获得cpu核数
                });
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            pool.shutdown();  //关闭线程池
        }
    }
}

建立可变线程数的线程池

public class juc_pooldemo {
    public static void main(String[] args) {
      ExecutorService pool = Executors.newCachedThreadPool();  //可变线程池，允许的最大数量为Integer.MAX
        try {
            for (int i = 0; i < 10; i++) {
                pool.execute(() -> {  //lanmbda表达式创建线程，并执行线程
                    System.out.println(Thread.currentThread().getName());
                    System.out.println(Runtime.getRuntime().availableProcessors());  //获得cpu核数
                });
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            pool.shutdown();  //关闭线程池
        }
    }
}

小结

ExecutorService pool =Executors.newSingleThreadExecutor();  //单个线程的线程池 
ExecutorService pool = Executors.newFixedThreadPool(5);  //固定数量的线程池
ExecutorService pool = Executors.newCachedThreadPool();  //可变线程池，允许的最大数量为Integer.MAX

2.自定义线程池

public class juc_pooldemo {
    public static void main(String[] args) {
      ExecutorService pool = new ThreadPoolExecutor(2,7,10,
                   TimeUnit.MILLISECONDS,new ArrayBlockingQueue<>(3));//用ThreadPoolExecutor自定义线程池
        try {
            for (int i = 0; i < 10; i++) {
                pool.execute(() -> {  //lanmbda表达式创建线程，并执行线程
                    System.out.println(Thread.currentThread().getName());
                    System.out.println(Runtime.getRuntime().availableProcessors());  //获得cpu核数
                });
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            pool.shutdown();  //关闭线程池
        }
    }
}

ThreadPoolExecutor7大参数

public ThreadPoolExecutor(int corePoolSize,  //核心线程数
                              int maximumPoolSize,  //最大线程数
                              long keepAliveTime,  //存活时间
                              TimeUnit unit,  //存活时间单位
                              BlockingQueue workQueue,  //阻塞队列
                              ThreadFactory threadFactory,  //线程工厂
                              RejectedExecutionHandler handler)  //拒绝服务策略

四种拒绝服务策略

3.线程池执行线程

ExecuteService pool = Executors.newfixedThreadPool(5);
pool.execute(new Runnable(){
//业务代码
});
//FutureTask futuretask = new FutureTask(new callable(){
//业务代码
//});  //callable接口实现多线程
//pool.execute(futuretask)；
//  E temp=futuretask.get(); //获取线程返回数据
pool.shutdown();  //关闭线程池一般放在finally语句块中

线程池的使用

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