package chapter2;

/**
 * 这是一个错误的加锁方式
 * <p/>
 * Created by 13 on 2017年5月4日.
 */
public class BadLockOnInteger implements Runnable {

 public static Integer i = 0;
 static BadLockOnInteger instance = new BadLockOnInteger();

 /**
 * When an object implementing interface <code>Runnable</code> is used
 * to create a thread, starting the thread causes the object's
 * <code>run</code> method to be called in that separately executing
 * thread.
 * <p/>
 * The general contract of the method <code>run</code> is that it may
 * take any action whatsoever.
 *
 * @see Thread#run()
 */
 @Override
 public void run() {
 for (int j = 0; j < 1000000; j++) {
 synchronized (i) {//这里同步的并不是同一个对象,因为i是以Integer关键字创建的
 //正确做法应该是 synchronized (instance)
 i++;
 }
 }
 }

 /**
 * 得到的结果并不是2000000,在多线程的操作中出现了错误
 *
 * @param args
 * @throws InterruptedException
 */
 public static void main(String args[]) throws InterruptedException {
 Thread thread1 = new Thread(instance);
 Thread thread2 = new Thread(instance);
 thread1.start();
 thread2.start();
 thread1.join();
 thread2.join();
 System.out.println(i);
 }
}