创建四个线程，两个线程对i加1，两个线程对i减1

package com.dairui.chars;

public class ThreadTest {
	public static void main(String[] args) {
		ThreadDemo1 threadDemo1 = new ThreadDemo1();

		ThreadDemo1.A a = threadDemo1.new A();
		ThreadDemo1.B b1 = threadDemo1.new B();

		Thread thread = null;

		for (int i = 0; i < 2; i++) {
			thread = new Thread(a);
			thread.start();
			thread = new Thread(b1);
			thread.start();
		}
	}

}

class ThreadDemo1 {
	static int i = 2;

	private synchronized void add() {
		// TODO Auto-generated method stub
		i++;
		System.out.println("线程" + Thread.currentThread().getName() + "A" + i);

	}

	private synchronized void reduce() {
		// TODO Auto-generated method stub
		i--;
		System.out.println("线程" + Thread.currentThread().getName() + "B" + i);

	}

	public class A extends Thread {

		public void run() {
			for (int i = 0; i < 10; i++) {
				add();
			}

		}

	}

	public class B extends Thread {

		public void run() {
			for (int i = 0; i < 10; i++) {
				reduce();
			}

		}

	}

}