public?class?Program?{ ????public??static?Tuser??user?=?new?Tuser(); ????public?static?void?main(String[]?args)?throws?InterruptedException?{ ????????new?Thread( ????????????????new?Runnable(){ ????????????????????public?void?run(){ ????????????????????????while(true){ ????????????????????????????String?s?=?get(); ????????????????????????????if?(user.getUsername().equals("hehe"))?{ ????????????????????????????????System.out.println("成功"); ????????????????????????????????//break; ????????????????????????????} ????????????????????????} ????????????????????} ????????????????} ????????).start(); ????????Thread.sleep(1000); ????????new?Thread(new?Runnable(){ ????????????@Override ????????????public?void?run(){ ????????????????user.setUsername("hehe"); ????????????????user=null; ????????????} ????????}).start(); ????} ????public?static?synchronized???String?get(){ ????????return?user.getUsername(); ????} }三個漸進式問題： 1.執行后什么結果 2 為什么? 3 去掉get方法的synchronized會怎么樣？