线程状态BLOKED的问题

Question

public class MyThread extends Thread{
    @Override
    public void run() {
        System.out.println("running....");
    }

    public static void main(String[] args) throws InterruptedException {
        MyThread t = new MyThread();
        log(t);
        t.start();
        log(t);
        for (int i = 0; i < 50; i++) {
            log(t);
        }
    }
    public static void log(Thread thread){
        System.out.println("Thread status is: " + thread.getState());
    }
}

打印的结果为：

Thread status is: NEW
Thread status is: RUNNABLE
Thread status is: RUNNABLE
Thread status is: RUNNABLE
Thread status is: RUNNABLE
Thread status is: RUNNABLE
Thread status is: BLOCKED
Thread status is: BLOCKED
running....
Thread status is: RUNNABLE
Thread status is: TERMINATED
Thread status is: TERMINATED

为什么线程启动后为经历BLOKED的状态呢？

Answer 1

CPU资源有限，线程运行需要占用CPU资源，目前一般线程运行都是采用抢占CPU的机制，系统给每个线程分配时间片，在某个时间片内执行某个线程。若是CPU核数少，开启的系统资源多，启动的线程就会经历Blocked状态。