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一道线程的面试题
线程1循环3次,线程2循环6次,线程3循环9次,接着又回到线程1循环3次,线程2循环6次,线程3循环9次...如此循环50次
1 package ch03; 2 3 import java.util.concurrent.locks.Condition; 4 import java.util.concurrent.locks.Lock; 5 import java.util.concurrent.locks.ReentrantLock; 6 7 public class ConditionCommunication { 8 9 public static void main(String[] args) { 10 final Business business = new Business(); 11 //线程1 12 new Thread(new Runnable() { 13 14 @Override 15 public void run() { 16 for(int i=1; i<=50; i++){ 17 business.sub1(i); 18 } 19 } 20 }).start(); 21 22 //线程2 23 new Thread(new Runnable() { 24 25 @Override 26 public void run() { 27 for(int i=1; i<=50; i++){ 28 business.sub2(i); 29 } 30 } 31 }).start(); 32 33 //主线程 34 for(int i=1; i<=50; i++){ 35 business.sub3(i); 36 } 37 38 } 39 40 } 41 42 /** 43 * 将相似的业务代码封装在同一个类中 44 * 45 */ 46 class Business{ 47 48 private Lock lock = new ReentrantLock(); 49 //标志位,1:表示线程1执行;2表示线程2执行;3表示线程3执行 50 volatile int flag = 1; 51 //条件 52 private Condition condition1 = lock.newCondition(); 53 private Condition condition2 = lock.newCondition(); 54 private Condition condition3 = lock.newCondition(); 55 56 public void sub1(int i){ 57 lock.lock(); 58 59 while(flag != 1){ 60 try { 61 condition1.await(); //线程1等待 62 } catch (InterruptedException e) { 63 e.printStackTrace(); 64 } 65 } 66 for(int j=1; j<=3; j++){ 67 System.out.println("sub1 "+j+",loop "+i); 68 } 69 flag = 2; 70 //唤醒线程2 71 condition2.signal(); 72 73 lock.unlock(); 74 } 75 76 public void sub2(int i){ 77 lock.lock(); 78 79 while(flag != 2){ 80 try { 81 condition2.await(); //线程2等待 82 } catch (InterruptedException e) { 83 e.printStackTrace(); 84 } 85 } 86 for(int j=1; j<=6; j++){ 87 System.out.println("sub2 执行"+j+"次,外部循环"+i); 88 } 89 flag = 3; 90 //唤醒线程3 91 condition3.signal(); 92 93 lock.unlock(); 94 } 95 96 public void sub3(int i){ 97 lock.lock(); 98 99 while(flag != 3){ 100 try { 101 condition3.await(); //线程3等待 102 } catch (InterruptedException e) { 103 e.printStackTrace(); 104 } 105 } 106 for(int j=1; j<=9;j++){ 107 System.out.println("sub3 执行"+j+"次,外部循环............"+i); 108 } 109 flag = 1; 110 //唤醒线程1 111 condition1.signal(); 112 113 lock.unlock(); 114 } 115 116 }
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