java多線程中的join()、 sleep()、 yield()、 wait()函數__函數

join()

當線程t1調用t2.join()後，t1保持鎖對象，等待t2執行完，t1進入可執行狀態；

package thread;public class JoinRunnable implements Runnable {Thread t1 ,t2;public JoinRunnable() {t1 = new Thread(this);t1.setName("t1");t2 = new Thread(this);t2.setName("t2");}@Overridepublic void  run() { //如果加上synchronized鎖標記，那麼即使t1線程調用了t2.join()；由於join不釋放鎖，t2還是無法按預期執行             System.out.println(Thread.currentThread().getName());                           if(Thread.currentThread()==t1){////////             try {            System.out.println("t2.join();");t2.join();/////////////////} catch (InterruptedException e) {e.printStackTrace();}             }                          for (int i = 0; i < 10; i++) {             System.out.println(Thread.currentThread().getName()); }}public static void main(String[] args){JoinRunnable runnable = new JoinRunnable();runnable.t1.start();runnable.t2.start();}}

運行結果：

t1t2t2.join();t2t2t2t2t2t2t2t2t2t2t1t1t1t1t1t1t1t1t1t1

---------------------------------------------------------------------------------------------------------------------------- sleep()

線上程t1中調用sleep(time),t1保持鎖對象，進入阻塞狀態，time完成後，t1進入可執行狀態。給了低優先順序線程執行的機會。

package thread;public class SleepRunnable implements Runnable {@Overridepublic synchronized void  run() { for(int i=0; i<3; i++){              System.out.println(Thread.currentThread().getName()+":"+i);              try{                  Thread.sleep(100);//線程調用了sleep(100)，由於sleep不釋放鎖，其它線程依然無法進入run函數             }              catch(InterruptedException e){                  System.out.println("Interrupted");              }          } }public static void main(String[] args){SleepRunnable myrun = new SleepRunnable();Thread t1 = new Thread(myrun);t1.setName("t1");Thread t2 = new Thread(myrun);t2.setName("t2");t1.start();t2.start();}}

運行結果：

t1:0t1:1t1:2t2:0t2:1t2:2

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yield()

當線程調用yield()，線程直接進入可執行狀態，不放鎖

package thread;public class YieldRunnable implements Runnable {@Overridepublic void  run() { //這裡如果用synchronized標記，則其它線程無法進入 for(int i=0; i<3; i++){              System.out.println(Thread.currentThread().getName()+":"+i);              Thread.yield();<span style="white-space:pre"></span>//////////////         } }public static void main(String[] args){YieldRunnable myrun = new YieldRunnable();Thread t1 = new Thread(myrun);t1.setName("t1");Thread t2 = new Thread(myrun);t2.setName("t2");t1.start();t2.start();}}

運行結果:

t1:0t2:0t1:1t2:1t1:2t2:2

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wait()

當現在t1在調用wait()後，線程釋放擁有的鎖，進入線程等待池。當其他線程調用notify時，JVM從線程等待池中取走某一線程，放入鎖標誌等待池。

package thread;public class WaitRunnable implements Runnable {Thread t1 ,t2;public WaitRunnable() {t1 = new Thread(this);t1.setName("t1");t2 = new Thread(this);t2.setName("t2");}@Overridepublic synchronized void  run() {             if(Thread.currentThread()==t1){            System.out.println("----------"+Thread.currentThread().getName()+" wait 10");try {wait(10);<span style="white-space:pre"></span>////////////} catch (InterruptedException e) {e.printStackTrace();}             }             for (int i = 0; i < 10; i++) {             System.out.println(Thread.currentThread().getName()); }             if(Thread.currentThread()==t2){             System.out.println("---------- t2 done");             notifyAll();<span style="white-space:pre"></span>////////////             }else{             System.out.println("---------- t1 done");             }}public static void main(String[] args){WaitRunnable runnable = new WaitRunnable();runnable.t1.start();runnable.t2.start();}}

運行結果：

----------t1 wait 10t2t2t2t2t2t2t2t2t2t2---------- t2 donet1t1t1t1t1t1t1t1t1t1---------- t1 done