**1. 创建线程 **
1.1 通过构造函数:public Thread(Runnable target, String name){} 或:public Thread(Runnable target){}
示例:
1. Thread thread1 = new Thread(new MyThread(), "mythread");2. class MyThread extends Thread(){3. public void run(){4. System.out.println("My First Thread');5. }6. }
1.2 直接实现Runnable接口:
示例:
1. Thread thread2 = new Thread(new Runnable{}{2. public void run(){3. System.out.println("This is my thread.");4. }5. });
**2. 运行线程 **
thead1.start()
3. sleep
1. try{2. #休眠1000ms3. Thread.sleep(1000);4. }catch(InterruptedException e){5. e.printStackTrace();6. }
4. getName() 获取线程名字, getId()获取线程id
System.out.println(Thread.currentThread().getName() + “:”+ Thread.currentThread().getId);
5. 停止线程,
千万不用stop(),stop会立即终止线程。
通过interrupt()中断线程,但是中断并没有停止线程,配合异常来实现:
1. public class Main {2. public static void main(String[] args) throws InterruptedException {3. try{4. Thread thread1=new Thread(new TheThread(),"thread1");5. thread1.start();6. Thread.sleep(2000);7. thread1.interrupt();8. }catch (InterruptedException e){9. e.printStackTrace();10. }11. }12. }13. class TheThread extends Thread{14. public void run() {15. super.run();16. for (int i = 0; i < 10; i++) {17. if(this.interrupted()){18. break;19. }20. System.out.println(Thread.currentThread().getName() + ":" + i);21. }22. }23. }
注意,如果在TheThread类里加入catch InterruptException的话,可能会导致interrupt被捕获,而绕过if(this.interrupted())的判断而无法终止线程。
6. 等待和通知
线程等待:当前线程就处于等待状态,直到其他线程调用了notify()方法,线程才会继续执行
1. public final void wait() throws InterruptedException
线程通知:
1. public final native void notify()
注意:在notify()方法后,当前线程不会马上释放该对象锁,要等到执行notify()方法的线程将程序执行完,也就是退出同步代码块中。
1. package wait.notify;3. public class ThreadWaitNotifyTest {4. final static Object object=new Object();5. public static class T1 extends Thread{6. public void run(){7. System.out.println(System.currentTimeMillis()+": T1 start");8. synchronized (object){9. try {10. System.out.println(System.currentTimeMillis()+": T1 wait");11. object.wait();12. } catch (InterruptedException e) {13. e.printStackTrace();14. }15. }16. System.out.println(System.currentTimeMillis()+": T1 end");17. }18. }19. public static class T2 extends Thread{20. public void run(){21. System.out.println(System.currentTimeMillis()+": T2 start");22. synchronized (object){23. System.out.println("T2 synchonized code start.");24. object.notify();25. try {26. Thread.sleep(2000);27. } catch (InterruptedException e) {28. e.printStackTrace();29. }finally{30. System.out.println("T2 synchonized code end.");31. }33. }34. try {35. Thread.sleep(2000);36. } catch (InterruptedException e) {37. e.printStackTrace();38. }39. System.out.println(System.currentTimeMillis()+": T2 end");40. }41. }42. public static void main(String[] args){43. Thread thread1=new T1();44. Thread thread2=new T2();45. thread1.start();46. thread2.start();47. }48. }
输出结果:
7. 线程优先级
高优先级的线程将会获得更多的CPU资源。一共分为10个优先级。
public final void setPriority(int newPriority)
源码分析:
1. public final void setPriority(int newPriority) {2. ThreadGroup g;3. checkAccess();4. if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {5. throw new IllegalArgumentException();6. }7. if((g = getThreadGroup()) != null) {8. if (newPriority > g.getMaxPriority()) {9. newPriority = g.getMaxPriority();10. }11. setPriority0(priority = newPriority);12. }13. }
1. public final static int MIN_PRIORITY = 1;2. public final static int NORM_PRIORITY = 5;3. public final static int MAX_PRIORITY = 10;
可见线程最高优先级为10, 最低为1, 默认为5.
当设定的newPriority高于该线程组ThreadGroup的最高Priority时,只能分配该线程组的最高Priority
8. 守护线程
类似守护进程,Java存在两种线程:用户线程和守护线程。它是一种特殊线程,执行的是一种后台服务,当一个系统中不存在非守护线程的时候,守护线程会自己销毁。典型的守护线程:JVM的垃圾回收线程。
public final void setDaemon(boolean on)
示例:
1. public class Main {2. public static void main(String[] args) throws InterruptedException {3. TheThread theThread=new TheThread();4. theThread.setDaemon(true);//设置守护线程5. theThread.start();6. Thread.sleep(5000);7. System.out.println("全都退出啦");8. }9. public static class TheThread extends Thread{10. public void run(){11. int i = 0;12. while (true){13. i++;14. System.out.println(Thread.currentThread().getId()+":"+i);15. try {16. Thread.sleep(2000);17. } catch (InterruptedException e) {18. e.printStackTrace();19. }20. }21. }22. }23. }
源码分析:
设置线程为用户线程(user thread)或守护线程(daemon thread),当剩余运行的线程均为守护线程时,JVM会退出。
1. public final void setDaemon(boolean on) {2. checkAccess();3. if (isAlive()) {4. throw new IllegalThreadStateException();5. }6. daemon = on;7. }
其中checkAccesss()方法如下:
1. public final void checkAccess() {2. SecurityManager security = System.getSecurityManager();3. if (security != null) {4. security.checkAccess(this);5. }6. }
该方法用于判断当前运行的线程是否有修改此线程的权限。
而public final native boolean isAlive();用于判断该线程是否处于alive状态,即该线程是否已经start,且没有die。
当isAlive的话就会抛出IllegalThreadStateException异常。
所以,设置守护线程的方法,逻辑就是先判断当前线程是否有修改的权限,再判断是否处于alive状态,如果不处于alive状态,则根据boolean变量on的值更改它的状态,即true:设为daemon线程,false:设为user线程。