Thread-线程的写法

public class 线程的加加减减 {

	 a a1 = new a();
	public static void main(String[] args) {
	  new 	线程的加加减减().call();
	}
   public   void call(){
	   for(int i=0;i<20;i++){
		   new Thread(new Runnable(){public void run(){ a1.jia();}}).start();    //第一种
		   new Thread(
				   new Runnable(){
					   public void run(){
							   a1.jian();
					   }
				   }).start();                                                                           //第二种
	   }
   }
}

class a {
	private int i=0;
	public synchronized void jia(){                               //同步
		i++;
		System.out.print(i);
	}

	public  synchronized void jian(){
		i--;
		System.out.print(i);
	}
}