2个问题：

1. str字段在两个A类型的实例之间共享[第2行]
2. 根据以下代码有什么含义？

class A implements Runnable {
    String str = "hello"; // line 2.

    public void run(){
        Synchronized(str){
            System.out.println(str+" "+Thread.currentThread().getName());
            Thread.sleep(100);
            System.out.println(str+" "+Thread.currentThread().getName());
            //anything
        }
    }

    public void static main(String[] args){  
        Thread one = new Thread(new A(),"one").start();  
        Thread two = new Thread(new A(),"two").start();  
    }
}