4线程，2个对i加，2个对i减

package test1;


/**
 * 设计4个线程，其中2个线程，每次对i加1，另外两个线程，每次对i减一
 * 
 * @author Administrator
 *
 */
public class Thread2 {
	public static void main(String[] args) {
		ShareData d = new ShareData();
		for (int i = 0; i < 2; i++) {
			new Thread(new Runnable1(d)).start();
			new Thread(new Runnable2(d)).start();
		}
	}
}

/**
 * 加
 * @author Administrator
 *
 */
class Runnable1 implements Runnable {
	private ShareData d;
	public Runnable1 (ShareData d) {
		this.d = d;
	}
	
	@Override
	public void run() {
		d.increment();
	}
}

/**
 * 减
 * @author Administrator
 *
 */
class Runnable2 implements Runnable {
	private ShareData d;
	public Runnable2 (ShareData d) {
		this.d = d;
	}
	
	@Override
	public void run() {
		d.decrement();
	}
}


class ShareData {

	private int i = 0;
	
	public synchronized void increment () {
		i++;
		System.out.println("加后i为：" + i);
	}
	
	public synchronized void decrement () {
		i--;
		System.out.println("减后i为：" + i);
	}
}package test1;


/**
 * 设计4个线程，其中2个线程，每次对i加