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合适些
    public static ArrayList singleElement(ArrayList al){
      //定义一个临时容器
      ArrayList newAl = new ArrayList();
      //在迭代是循环中next调用一次，就要hasNext判断一次
      Iterator it = al.iterator();

       while (it.hasNext()){
         Object obj = it.next();//next()最好调用一次就hasNext()判断一次否则容易发生异常

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