問題：3個執行緒按順序列印ABC,A執行緒列印A,B執行緒列印B,C執行緒列印C.

實現一：使用synchronized關鍵字：

package com.Thread;
import java.util.concurrent.atomic.AtomicInteger;
/**
 * Created by Administrator on 2018/3/25 0025.
 */
public class Print implements Runnable

{
  private static AtomicInteger count = new AtomicInteger(0);
  public static void 
 
main ( String args[] ) {
    Print p1 = new Print();
Print p2 = new Print();
Print p3 = new Print();
Thread t1 = new Thread(p1);
Thread t2 = new Thread(p2);
Thread t3 = new Thread(p3);
t1.start();
t2.start();
t3.start();
}

  public void run () {
    while (true) {
      synchronized (count) {
        try 
 
{
          if (count.get() % 3 == 0) {
            System.out.print("A");
} else if (count.get() % 3 == 1) {
            System.out.print("B");
} else {
            System.out.print("C");
}
          count.set(count.get() + 1);
count.notifyAll();
count.wait();
} catch (InterruptedException e) {
          e.printStackTrace();
 
}
      }
    }
  }
} 

實現二：使用重入鎖+Condition

package com.Thread;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
 * Created by Administrator on 2018/3/25 0025.
 */
public class Print1 implements Runnable {
  static Lock lock = new ReentrantLock();
  static Condition c1 = lock.newCondition();
  static Condition c2 = lock.newCondition();
  static Condition c3 = lock.newCondition();
  static Integer aa=1;
  public static void main ( String args[] ) {

    new Thread(new Print1()).start();
    new Thread(new Print1()).start();
    new Thread(new Print1()).start();
}

  public void run () {
    for (int i = 1; i < 4; i++) {

        if (aa % 3 == 1) {
          try {
        lock.lock();
System.out.print("A");
++aa;
c2.signal();
c1.await();
} catch (InterruptedException e) {
          e.printStackTrace();
}finally {
          lock.unlock();
}
      }
      else if (aa % 3 == 2) {
        try {
        lock.lock();
System.out.print("B");
++aa;
c3.signal();
c2.await();
} catch (InterruptedException e) {
          e.printStackTrace();
}finally {
          lock.unlock();
}
      }
      else if (aa % 3 == 0) {
        try {
          lock.lock();
System.out.print("C");
++aa;
c1.signal();
c3.await();
} catch (InterruptedException e) {
          e.printStackTrace();
}finally {
          lock.unlock();
}
      }
    }
  }
}