java多线程之间的相互通信

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

public class Demo {

private int signal;

Lock lock = new ReentrantLock();
Condition a = lock.newCondition();
Condition b = lock.newCondition();
Condition c = lock.newCondition();

public void a() {
lock.lock();
while(signal != 0 ) {
try {
a.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("a");
signal ++;
b.signal();
lock.unlock();
}

public  void b() {
lock.lock();
while(signal != 1) {
try {
b.await();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println("b");
signal ++;
c.signal();
lock.unlock();
}

public  void c () {
lock.lock();
while(signal != 2) {
try {
c.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("c");
signal = 0;
a.signal();
lock.unlock();
}

public static void main(String[] args) {

Demo d = new Demo();
A a = new A(d);
B b = new B(d);
C c = new C(d);

new Thread(a).start();
new Thread(b).start();
new Thread(c).start();

}
}

class A implements Runnable {

private Demo demo;

public A(Demo demo) {
this.demo = demo;
}

@Override
public void run() {
while(true) {
demo.a();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}

}
class B implements Runnable {

private Demo demo;

public B(Demo demo) {
this.demo = demo;
}

@Override
public void run() {
while(true) {
demo.b();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}

}
class C implements Runnable {

private Demo demo;

public C(Demo demo) {
this.demo = demo;
}

@Override
public void run() {
while(true) {
demo.c();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}

}