public class MyService
{
private int flag = 1;
public synchronized void printA(){
while (flag != 1)
{
try
{
this.wait();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
System.out.print(Thread.currentThread().getName());
flag = 2;
this.notifyAll();
}
public synchronized void printB(){
while (flag != 2)
{
try
{
this.wait();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
System.out.print(Thread.currentThread().getName());
flag = 3;
this.notifyAll();
}
public synchronized void printC(){
while (flag != 3)
{
try
{
this.wait();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
System.out.print(Thread.currentThread().getName());
flag = 1;
this.notifyAll();
}
}
测试代码:
package testABC;
public class TestMain
{
public static void main(String[] args)
{
//编写一个程序,启动三个线程,三个线程的ID分别是A,B,C;,每个线程将自己的ID值在屏幕上打印5遍,打印顺序是ABCABC...
// MyService service = new MyService();
MyService2 service = new MyService2();
Thread A = new Thread(new Runnable()
{
@Override
public void run()
{
for (int i = 0; i < 5; i++)
{
service.printA();
}
}
});
A.setName("A");
Thread B = new Thread(new Runnable()
{
@Override
public void run()
{
for (int i = 0; i < 5; i++)
{
service.printB();
}
}
});
B.setName("B");
Thread C = new Thread(new Runnable()
{
@Override
public void run()
{
for (int i = 0; i < 5; i++)
{
service.printC();
}
}
});
C.setName("C");
A.start();
B.start();
C.start();
}
}
使用Lock实现:
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class MyService2
{
private int flag = 1;
private Lock lock = new ReentrantLock();
private Condition conditionA = lock.newCondition();
private Condition conditionB = lock.newCondition();
private Condition conditionC = lock.newCondition();
public void printA()
{
try
{
lock.lock();
if (flag != 1)
{
try
{
conditionA.await();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
System.out.print(Thread.currentThread().getName());
flag = 2;
conditionB.signal();
}
finally
{
lock.unlock();
}
}
public void printB()
{
try
{
lock.lock();
if (flag != 2)
{
try
{
conditionB.await();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
System.out.print(Thread.currentThread().getName());
flag = 3;
conditionC.signal();
}
finally
{
lock.unlock();
}
}
public void printC()
{
try
{
lock.lock();
if (flag != 3)
{
try
{
conditionC.await();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
}
System.out.print(Thread.currentThread().getName());
flag = 1;
conditionA.signal();
}
finally
{
lock.unlock();
}
}
}
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