fork/join 和开线程数量

//四个线程同时去执行
ForkJoinPool myPool = new ForkJoinPool(4);
myPool.submit(() -> {})

打开的线程数

public class ThreadPoolHelper {

    public static ThreadPool instance;
    private ThreadPoolExecutor longExecutor; // 耗时比较长的线程池   用来请求网络
    private ThreadPoolExecutor shortExecutor; // 比较短的线程池    用来加载本地数据

    // 获取单例的线程池对象
    public static ThreadPool getInstance() {
        if (instance == null) {
            synchronized (ThreadPoolHelper.class) {
                if (instance == null) {
                    int cpuNum = Runtime.getRuntime().availableProcessors();// 获取处理器数量
                    int threadNum = cpuNum * 2 + 1;// 根据cpu数量,计算出合理的线程并发数
                    instance = new ThreadPool(threadNum-1, threadNum, Integer.MAX_VALUE);//默认是双核的cpu 每个核心走一个线程 一个等待线程
                }
            }
        }
        return instance;
    }

    public static class ThreadPool {
        private ThreadPoolExecutor mExecutor;
        private int corePoolSize;// 核心线程数
        private int maximumPoolSize;// 最大线程数
        private long keepAliveTime;// 闲置线程存活时间

        private ThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime) {
            this.corePoolSize = corePoolSize;
            this.maximumPoolSize = maximumPoolSize;
            this.keepAliveTime = keepAliveTime;
        }

        public void execute(Runnable runnable) {
            if (runnable == null) {
                return;
            }
            if (mExecutor == null) {
                mExecutor = new ThreadPoolExecutor(corePoolSize,// 核心线程数
                        maximumPoolSize, // 最大线程数
                        keepAliveTime, // 闲置线程存活时间
                        TimeUnit.MILLISECONDS,// 时间单位
                        new LinkedBlockingDeque<Runnable>(Integer.MAX_VALUE),// 线程队列
                        Executors.defaultThreadFactory(),// 线程工厂
                        new ThreadPoolExecutor.AbortPolicy() {// 队列已满,而且当前线程数已经超过最大线程数时的异常处理策略
                            @Override
                            public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
                                super.rejectedExecution(r, e);
                            }
                        }
                );
            }
            mExecutor.execute(runnable);
        }


        // 从线程队列中移除对象
        public void cancel(Runnable runnable) {
            if (mExecutor != null) {
                mExecutor.getQueue().remove(runnable);
            }
        }
    }


    /**
     * 测试使用方法
     */
    @Test
    public void test(){

        ThreadPoolHelper.getInstance().execute(new Runnable(){
            public void run() {
                //这里编写处理业务代码

            }

        });
    }