线程状态

Thread.state

New	尚未启动的线程处于此状态
Runnable	在java虚拟机中执行的线程处于此状态
Blocked	被阻塞等待监视器锁定的线程处于此状态
Waiting	正在等待另一个线程执行特定动作的线程处于此状态
Time_Waiting	正在等待另一个线程执行动作达到指定等待时间的线程处于此状态
Terminated	已退出的线程处于此状态

package Thread;/*** @author zxy* 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) {// TODO Auto-generated catch blocke.printStackTrace();}}System.out.println("");});/* 观察状态 */Thread.State state = thread.getState();System.out.println(state);/* 观察启动后 */thread.start();//启动线程state = thread.getState();System.out.println(state);//run/* 只要线程不终止，就一直输出状态 */while(state != Thread.State.TERMINATED) {Thread.sleep(100);/* 更新线程状态 */state = thread.getState();System.out.println(state);}}
}

输出：

NEW
RUNNABLE
TIMED_WAITING
TIMED_WAITING

·········

TIMED_WAITING

TERMINATED

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线程优先级

• 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，线程调度器按照优先级决定应该调度哪个线程来执行
• 线程的优先级用数字表示，范围从1-10
  • Thread.MIN_PRIORITY = 1;
  • Thread.MAX_PRIORITY = 10;
  • Thread.NORM_PRIORITY = 5;
• 使用以下方式改变或获取优先级：
  • getPriority().setPriority(int xxx)
• 优先级的设定建议在start调度前
• 优先级低只是意味着获得调度的概率低，并不是优先级低就不会被调用了，这都是看CPU的调度

package Thread;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);/* 先设置优先级 再启动start方法 */t1.start();t2.setPriority(1);t2.start();t3.setPriority(Thread.MAX_PRIORITY);t3.start();t4.setPriority(8);t4.start();t5.setPriority(Thread.MAX_PRIORITY);t5.start();}}class MyPriority implements Runnable{@Overridepublic void run() {// TODO Auto-generated method stubSystem.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());}}

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守护线程

• 线程分为用户线程和守护线程
• 虚拟机必须确保用户线程执行完毕
• 虚拟机不用等待守护线程执行完毕
• 如 后台记录操作日志、监控内存、垃圾回收等待