(四)、五大线程状态
14.状态顺序
15.线程方法
1.setPriority( int newOriority) 更改线程优先级 2.static void sleep (long mills) 在指定的毫秒内礼让数据 3.void join() 等待该进程终止 4.static void yield() 暂停当前正在执行的线程对象，并执行其他线程 5.void interrupt() 中断线程，别用这个方式 6.boole isAlive() 测试线程是否处于活动状态
15.1停止线程(false)
1.不推荐使用JDK提供的stop()、destory()方法 2.推荐线程自己停止下来 3.建议使用一个标志位进行终止变量，即flag=false;
public class Demo9 implements Runnable{ //1.设置一个标识位 private boolean flag=true; @Override public void run() { int i=0; while (flag){ System.out.println("run......thread "+i++); } } public void stop(){ this.flag=false; } public static void main(String[] args) { Demo9 demo9=new Demo9(); //1.开启线程 new Thread(demo9).start(); for (int i = 0; i <1000 ; i++) { if (i==900){ //调用stop方法进行线程停止 demo9.stop(); System.out.println("线程已经停止"); } System.out.println("main "+i); } } }
15.2线程休眠(sleep)
1.sleep() 指定当前线程阻塞的毫秒数 2.sleep()存在异常interruptedException; 3.sleep时间达到后线程就进入就绪状态 4.sleep可以模拟网络延时，倒计时等 (放大问题的发生性) 5.每个对象都有一个锁，sleep不会释放锁
利用线程模拟倒计时的操作:
import java.text.SimpleDateFormat; import java.util.Date; import java.util.SimpleTimeZone; public class Demo10 { public static void main(String[] args) throws Exception { // tendown(); //打印系统当前时间 Date start=new Date(System.currentTimeMillis()); while (true){ try { Thread.sleep(1000); System.out.println(new SimpleDateFormat("HH:mm:ss").format(start)); //打印时间 start=new Date(System.currentTimeMillis()); //更新时间 } catch (Exception e) { e.printStackTrace(); } } } public static void tendown() throws Exception{ int num=10; while (true){ Thread.sleep(1000); System.out.println("倒计时:"+num--); if(num<=0){ break; } } } }
15.3线程礼让(yield)
1.礼让线程,让当前正在执行的线程暂停，但不阻塞 2.将线程从运行状态转为就绪状态 3.让cpu重新调度，礼让不一定成功。
public class Demo11 { public static void main(String[] args) { my_Yield my_yield=new my_Yield(); new Thread(my_yield,"A").start(); new Thread(my_yield,"B").start(); } } class my_Yield implements Runnable{ @Override public void run() { System.out.println(Thread.currentThread().getName()+"执行开始"); Thread.yield(); //礼让 System.out.println(Thread.currentThread().getName()+"执行结束"); } }
15.4线程强行执行(join)
1.join 合并线程，待此线程执行完成后，在执行其他的线程，其他线程阻塞 2.可以想象成vip
public class Demo12 implements Runnable{ @Override public void run() { try { Thread.sleep(100); } catch (InterruptedException e) { e.printStackTrace(); } for (int i=0;i<100;i++) { System.out.println("线程VIP来了"); } } public static void main(String[] args) throws Exception { Demo12 demo12=new Demo12(); Thread thread=new Thread(demo12); thread.start(); //主线程 for (int i = 0; i < 1000; i++) { if(i==200){ thread.join(); //插队 } System.out.println("main"+i); } } }
16.观测线程状态(Thread.stata)
详解: like=()->{ }; Thread thread=new Thread(like); thread.start();
public class Demo13 { public static void main(String[] args) { //利用lam 设置Thread 的抽象方法 Thread thread=new Thread(()->{ for (int i = 0; i < 5; i++) { try { Thread.sleep(1000); System.out.println("/"); } catch (InterruptedException e) { e.printStackTrace(); } } }); //观察状态 Thread.State state=thread.getState(); System.out.println(state); //NEW //观察 thread.start(); //启动线程 state=thread.getState(); //启动后i的状态 System.out.println(state); //RUN while (state!=Thread.State.TERMINATED){ //只要程序不重质，就一直输出 try { Thread.sleep(100); state=thread.getState(); //更新状态 System.out.println(state); //输出状态 } catch (InterruptedException e) { e.printStackTrace(); } } } }
17.线程优先级(Priority)
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多有线程，线程调度 器按照优先级决定因该调用哪个线程来执行. 2.线程的优先级用数字表示会 1-10; 3.使用以下方式改变或获取优先级 getPriority().setPriority(int xx) 优先级的设定建议放在start()调度前 优先级并不代表着一定先调用
public class Demo14 { public static void main(String[] args) { //1.查看主线程默认的优先级 System.out.println(Thread.currentThread().getName()+"--->"+Thread.currentThread().getPriority())； MyPriority myPriority=new MyPriority(); Thread thread_one=new Thread(myPriority); Thread thread_two=new Thread(myPriority); Thread thread_three=new Thread(myPriority); Thread thread_four=new Thread(myPriority); Thread thread_five=new Thread(myPriority); Thread thread_six=new Thread(myPriority); //设置优先级 thread_two.setPriority(1); thread_three.setPriority(4); thread_four.setPriority(Thread.MAX_PRIORITY); thread_five.setPriority(8); thread_six.setPriority(9); //线程开启 thread_one.start(); thread_two.start(); thread_three.start(); thread_four.start(); thread_five.start(); thread_six.start(); } } class MyPriority implements Runnable{ @Override public void run() { System.out.println(Thread.currentThread().getName()+"--->"+Thread.currentThread().getPriority()); } }
