错误原因就是:
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应该改为:
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输出正常：
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
A
B
C
import java.awt.image.VolatileImage;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class AABBCC {static Lock lock = new ReentrantLock();
final static Condition condition1 = lock.newCondition();
final static Condition condition2 = lock.newCondition();
final static Condition condition3 = lock.newCondition();
private volatile int state = 1;
public static void main(String[] args) {AABBCC aabbcc = new AABBCC();
Thread thread1 = new Thread(()->{
aabbcc.print("A",1,2,condition1,condition2);
});
Thread thread2 = new Thread(()->{
aabbcc.print("B",2,3,condition2,condition3);
});
Thread thread3 = new Thread(()->{
aabbcc.print("C",3,1,condition3,condition1);
});
thread1.start();
thread2.start();
thread3.start();
}public void print(String s,int flg,int nextState,Condition currentCondition,Condition nextCondition){
for(int i=0;
i<2;
i++){
try {
lock.lock();
if(flg == state){
System.out.println(s);
state = nextState;
nextCondition.signal();
}
currentCondition.await();
}catch (Exception e){
e.printStackTrace();
}finally {
lock.unlock();
}
}
}}
假如情况：thread1执行nextCondition.signal(); 后 thread2 thread3都已经执行完currentCondition.await();
state=1
假如外面的for循环 i<2 即循环2次:
thread1:
i=0 A signalThread2 本线程await
i=1 await A singal i=2 A singal i=3 A singal
当thread3 singal时 打印A 本线程wait
thread2:
i=0 本线程await
i=1 B singalThread3 本线程await
当thread1 singal时 打印B 本线程await
thread3:
i=0本线程await
i=1 C singalThread1 本线程await
那么打印结果是:
A
B
C
A
B
thread1 waiting
thread2 waiting
thread3 for循环进不去
所以最终结果是 线程1 线程2 死死地等待 程序结束不了
假如是非正常情况：thread1执行完nextCondition.signal(); ,thread2才开始执行if(flg == state){,thread2执行完的时候,thread3才开始执行if(flg == state){
等等情况
会打印出多种结果,但相同的是 程序都不会终止
比如以下打印结果都会出现,具体再分析原因吧,以上 只分析了2种情况:
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【Condition ReentrantLock循环10次打印ABC错误分析】
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