//僅用于測試，無任何業務public class DateFormat2 {    public static SimpleDateFormat parse(){        SimpleDateFormat  adf=new SimpleDateFormat ();      return adf}}//多線程測試上述方法,局部變量應該在線程棧中,每個線程訪問該方法后都new一個對象,應該是不同的引用地址,但結果卻不是,測試方法如下public class Test {  public static class TestSimpleDateFormatThreadSafe extends Thread {       @Override       public void run() {           while(true) {               try {                   this.join(2000);               } catch (InterruptedException e1) {                   e1.printStackTrace();               }                   try {System.out.println(this.getName()+":"+DateFormat2.parse());} catch (ParseException e) {e.printStackTrace();}           }       }      }public static void main(String[] args) throws ParseException {for (int i = 0; i <3; i++) {new TestSimpleDateFormatThreadSafe().start();}}}