class ArrayListTest1 {
    public static void main(String[] args) {
        ArrayList al = new ArrayList();
        al.add("java03");
        al.add("java03");
        al.add("java01");
        al.add("java02");
        al.add("java01");
        al.add("java02");
        al.add("java01");
        System.out.println(al);

        al = singleElement(al);
        System.out.println(al);

    }

    //返回List合適些
    public static ArrayList singleElement(ArrayList al){
      //定義一個臨時容器
      ArrayList newAl = new ArrayList();
      //在迭代是循環中next調用一次，就要hasNext判斷一次
      Iterator it = al.iterator();

       while (it.hasNext()){
         Object obj = it.next();//next()最好調用一次就hasNext()判斷一次否則容易發生異常

         if (!newAl.contains(obj))
            newAl.add(obj);
        }
        return newAl;
    }
}