Java并发编程——(4)观测线程状态+线程优先级

七、观测线程状态

//观察测试线程的状态
public class TestState {
	public static void main(String[] args) throws InterruptedException {
		Thread thread = new Thread(() -> {
			for (int i = 0; i < 5; i++) {
				try {
					Thread.sleep(1000);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
			System.out.println("--------");
		});
		// 观察状态
		Thread.State state = thread.getState();
		System.out.println(state);// NEW

		// 观察启动后
		thread.start();
		state = thread.getState();
		System.out.println(state);// Run

		while (state != Thread.State.TERMINATED) {// 只要线程不终止就一直输出状态
			Thread.sleep(100);
			state = thread.getState();// 更新线程状态
			System.out.println(state);// 输出状态
		}
	}
}

注：线程死亡后不可再次start。

八、线程优先级

1.Java提供一个线程调度器来监控程序中启动后进入就绪状态的所有线程，线程调度器安装优先级决定应该调度哪个线程来执行。
2.线程的优先级用数字表示，范围从1~10
(1)Thread.MIN_PRIORITY=1;
(2)Thread.MAX_PRIORITY=10;
(3)Thread.NORM_PRIORITY=5;
3.使用getPriority()和setPriority(int xxx)方法可以获取或改变线程优先级
4.优先级低只是意味着会获得调度的概率低，并不是优先级低就不会被调用了，这都是看CPU的调度

//测试线程优先级
public class TestPriority {
	public static void main(String[] args) {
		//主线程默认优先级
		System.out.println(Thread.currentThread().getName()+"--->"+Thread.currentThread().getPriority());
		MyPriority myPriority=new MyPriority();
		Thread t1=new Thread(myPriority);
		Thread t2=new Thread(myPriority);
		Thread t3=new Thread(myPriority);
		Thread t4=new Thread(myPriority);
		Thread t5=new Thread(myPriority);
		Thread t6=new Thread(myPriority);
		
		//先设置优先级，再启动
		t1.start();
		
		t2.setPriority(1);
		t2.start();
		
		t3.setPriority(4);
		t3.start();
		
		t4.setPriority(Thread.MAX_PRIORITY);
		t4.start();
		
		t5.setPriority(3);
		t5.start();
		
		t6.setPriority(9);
		t6.start();
	}
}
class MyPriority implements Runnable{
	@Override
	public void run() {
		System.out.println(Thread.currentThread().getName()+"--->"+Thread.currentThread().getPriority());
	}
}