练习-模拟多线程访问资源

package cn.edu.zsu.snippet.concurrent;

import java.util.logging.Logger;

import cn.edu.zsu.snippet.annotation.Run;

/**
* 用来演示线程安全、同步
*
* @author Justin
*
*/
public final class Synchronization {
/**
*
*/
private final Logger logger = Logger.getLogger(getClass().getName());

/**
* 演示线程不安全的object的并发
*/
private void unsafe() {
logger.info(String
.format("演示非线程安全object的方法入口 %s", getClass().getName()));
try {
Ten ten = new MultipleTen();
int counter = 0;
while (counter++ < 10000) {
Cracker c = new Cracker(ten);
Shouter s = new Shouter(ten);
c.start();
s.start();
}
} finally {

}
logger.info(System.getProperty("line.separator"));
}

/**
* 演示线程安全的object并发
*/
private void safe() {
logger.info(String.format("演示线程安全的object方法入口 %s", getClass().getName()));

try {
Ten ten = new SynchronizedMultipleTen(new MultipleTen());
int counter = 0;
while (counter++ < 1000) {
Cracker c = new Cracker(ten);
c.start();
// service.execute(c);
Shouter s = new Shouter(ten);
s.start();
// service.execute(s);
}
} finally {
}
logger.info(System.getProperty("line.separator"));
}

@Run
public void exec() {
logger.info(String.format("开始Synchronization的主函数 %s", getClass()
.getName()));
safe();
unsafe();

}
}

/**
* 用来演示的接口
*
* @author Justin
*
*/
interface Ten {
public void increment();

public int getCounter();
}

/**
* <pre>
* 非同步的Ten实现，方法体没有使用synchronized来进行限定
* counter 也没有用volatile来修饰
* </pre>
*
* @author Justin
*
*/
class MultipleTen implements Ten {
private int counter = 0;

/**
*
4000
<p>
* 通过十次独立的自增操作给counter增加值，这里是产生不同步的根源。
* </p>
* <p>
* 可能会在没有完全执行完十次操作，counter值就被getCounter() 拿出去打印了。
* </p>
*/
public void increment() {
counter++;
counter++;
counter++;
counter++;
counter++;
counter++;
counter++;
counter++;
counter++;
counter++;
}

public int getCounter() {
return counter;
}
}

/**
* Synchronized Decorator of "Ten"
*
* @author Justin
*
*/
class SynchronizedMultipleTen implements Ten {
private Ten ten;

private Object mutex;

public SynchronizedMultipleTen(Ten ten) {
this.ten = ten;
mutex = this;
}

@Override
public void increment() {
synchronized (mutex) {
ten.increment();
}
}

@Override
public int getCounter() {
synchronized (mutex) {
return ten.getCounter();
}
}
}

/**
* 负责给Ten进行增加操作。
*
* @author Justin
*
*/
class Cracker extends Thread {
// private final Logger logger = Logger.getLogger(getClass().getName());
private Ten ten;

public Cracker(Ten gen) {
this.ten = gen;
}

@Override
public void run() {
super.run();
ten.increment();
// logger.info(String.format("current value == %d", ten.getCounter()));
}
}

/**
* 负责打印一个Ten实例
*
* @author Justin
*
*/
class Shouter extends Thread {

private Ten ten;
private final Logger logger = Logger.getLogger(getClass().getName());

public Shouter(Ten ten) {
this.ten = ten;
}

@Override
public void run() {
final String pattern = "current value is : %d. it is not a multiple 10, produced by class : %s";
super.run();
int value = ten.getCounter();
if (!(value % 10 == 0))
logger.info(String.format(pattern, value, ten.getClass().getName()));
}
}