编写一个程序，开启3个线程，这3个线程的ID分别为A、B、C，每个线程将自己的ID在屏幕上打印10遍，要求输出结果必须按ABC的顺序显示；如：ABCABC

package test1;

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

/**
* 编写一个程序，开启3个线程，
* 这3个线程的ID分别为A、B、C，
* 每个线程将自己的ID在屏幕上打印10遍，
* 要求输出结果必须按ABC的顺序显示；
* 如：ABCABC….依次递推
*
* 设计：LOCK+condition(可以把A、B、C理解成主线程，子线程，孙线程)
* @author Mahone
*
*/
public class Test3 {
public static void main(String[] args) {
Test3 obj = new Test3();
obj.init();
}

private void init() {
final Test3Business tb = new Test3Business();

Thread t1 = new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 10; i++) {
tb.printA();
}
}
});
t1.setName("A");

Thread t2 = new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 10; i++) {
tb.printB();
}
}
});
t2.setName("B");

Thread t3 = new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 10; i++) {
tb.printC();
}
}
});
t3.setName("C");

t1.start();
t2.start();
t3.start();
}
}

class Test3Business {

private String flag = "A";

private Lock lock = new ReentrantLock();

private Condition cA = lock.newCondition();
private Condition cB = lock.newCondition();
private Condition cC = lock.newCondition();

public void printA () {
try {
lock.lock();
if (!flag.equals("A")) {
cA.await();
}
System.out.println(Thread.currentThread().getName());
Thread.sleep(1000);
flag = "B";
cB.signal();
} catch (Exception ex) {
ex.printStackTrace();
}finally {
lock.unlock();
}
}

public void printB () {
try {
lock.lock();
if (!flag.equals("B")) {
cB.await();
}
System.out.println(Thread.currentThread().getName());
Thread.sleep(1000);
flag = "C";
cC.signal();
} catch (Exception ex) {
ex.printStackTrace();
}finally {
lock.unlock();
}
}

public void printC () {
try {
lock.lock();
if (!flag.equals("C")) {
cC.await();
}
System.out.println(Thread.currentThread().getName());
Thread.sleep(1000);
flag = "A";
cA.signal();
} catch (Exception ex) {
ex.printStackTrace();
}finally {
lock.unlock();
}
}
}