需求：有三個執行緒輪流執行，第一個執行緒列印A，第二個執行緒列印B，第三個執行緒列印C……迴圈10次。

思路：三個執行緒對應三個Condition、三個Condition共享一個Lock、一個執行緒輪流狀態state。執行緒拿到鎖之後，通過state進行判斷，如果沒有輪到當前執行緒列印，則通過當前執行緒對應的Condition使當前執行緒進入等待狀態，並釋放鎖；如果輪到當前執行緒列印，則執行列印、更改state狀態以及通過下一個執行緒對應的Condition喚醒下一個執行緒；……迴圈10次。

效率：執行緒不滿足條件等待，滿足條件執行列印，並喚醒下一個執行緒，效率比較高。

實現程式碼：

package edu.self.multithread;

import
 
 java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Created by SunYanhui on 2017/12/7.
 */
public class MultipleThreadRotationUsingExplicitLockCondition {
    public static void main(String[] args) {
        PrintABCUsingCondition printABC = new
 
 PrintABCUsingCondition();
        new Thread(() -> printABC.printA()).start();
        new Thread(() -> printABC.printB()).start();
        new Thread(() -> printABC.printC()).start();
    }
}

class PrintABCUsingCondition {
    private Lock lock = new ReentrantLock();
    private Condition
 
 conditionA = lock.newCondition();
    private Condition conditionB = lock.newCondition();
    private Condition conditionC = lock.newCondition();
    private int state = 0;
    //private int attempts = 0;

    public void printA() {
        print("A", 0, conditionA, conditionB);
    }

    public void printB() {
        print("B", 1, conditionB, conditionC);
    }

    public void printC() {
        print("C", 2, conditionC, conditionA);
    }

    private void print(String name, int currentState, Condition currentCondition, Condition nextCondition) {
        for (int i = 0; i < 10; ) {
            lock.lock();
            try {
                //System.out.println(Thread.currentThread().getName()+" try to print "+name+", attempts : "+(++attempts));
                while (state % 3 != currentState) {
                    currentCondition.await();
                }
                System.out.println(Thread.currentThread().getName() + " print " + name);
                state++;
                i++;
                nextCondition.signal();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }
        }
    }
}