多线程核心4：线程的六种状态

状态转换图

• 一般把Blocked（被阻塞）、Waiting（等待）、Timed_waiting（计时等待）都称为阻塞状态
  
• 特殊情况：
  1. 从WAITING状态刚被唤醒时，通常不能立刻抢到monitor锁，这时就会从WAITING先进入BLOCKED状态，抢到锁之后再转换到RUNNABLE状态
  2. 如果在WAITING过程中，发生异常，直接跳到TERMINATION状态

六种状态具体代码

• 线程刚创建好，还未启动，这时属于NEW状态，线程处于就绪状态或者正在运行，都是属于RUNNABLE，运行结束，进入TERMINATED

  public class NewRunnableTerminated implements Runnable {
        
        
      @Override
      public void run() {
        
        
          for (int i = 0; i < 1000; i++) {
        
        
              System.out.println(i);
          }
      }
  
      public static void main(String[] args) {
        
        
          Thread thread = new Thread(new NewRunnableTerminated());
          System.out.println(thread.getState());//NEW
          thread.start();
          System.out.println(thread.getState());//RUNNABLE
          try {
        
        
              Thread.sleep(10);
          } catch (InterruptedException e) {
        
        
              e.printStackTrace();
          }
          System.out.println(thread.getState());//RUNNABLE
  
          try {
        
        
              Thread.sleep(100);
          } catch (InterruptedException e) {
        
        
              e.printStackTrace();
          }
          System.out.println(thread.getState());//TERMINATED
      }
  }
  

• 在thread1运行run方法时，具体操作是休眠1秒，处于BLOCKED状态，这时thread2运行run方法，但syn()方法是synchronized修饰的，thread1还没释放锁，thread2自然拿不到锁，进入计时等待TIMED_WAITING，当thread1休眠结束，马上执行wait()，thread2的状态变成等待WAITING

  public class BlockedWaitingTimedWaiting implements Runnable {
        
        
      @Override
      public void run() {
        
        
          try {
        
        
              syn();
          } catch (InterruptedException e) {
        
        
              e.printStackTrace();
          }
      }
  
      private synchronized void syn() throws InterruptedException {
        
        
          Thread.sleep(1000);
          wait();
      }
  
  
      public static void main(String[] args) throws InterruptedException {
        
        
          BlockedWaitingTimedWaiting runnable = new BlockedWaitingTimedWaiting();
          Thread thread1 = new Thread(runnable);
          thread1.start();
          Thread thread2 = new Thread(runnable);
          thread2.start();
          Thread.sleep(5);
          System.out.println(thread1.getState());//BLOCKED
          System.out.println(thread2.getState());//TIMED_WAITING
          Thread.sleep(1200);
          System.out.println(thread2.getState());//WAITING
      }
  }