java - 重复链表值

Question

我有一个链接列表，如果我每次插入一个对象，那么最后一个值就会重复。不是第一次插入，而是下一次插入，它重复1,6,16....请检查下面的代码

Java 代码:

    List<JSONObject> linkedList = new LinkedList<JSONObject>();

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out=response.getWriter();
        double ID =Double.parseDouble(request.getParameter("value1"));
        double  age=Double.parseDouble(request.getParameter("value2"));
        String type=request.getParameter("value5");
        int pre=Integer.parseInt(request.getParameter("value3"));
        int nxt=Integer.parseInt(request.getParameter("value4"));
        String config_Feature=request.getParameter("value6");

        try {
            if(config_Feature.equals("insert")) {
                int insertAtIndexForJSONArray = findInsertAtIndex(linkedList,nxt);

                insertValue(insertAtIndexForJSONArray,linkedList,ID,age,type);

                JSONArray alist = new JSONArray(linkedList);
                System.out.println(alist);
                WritingJsonDataToFile(alist);
            }
        }
        catch (JSONException e) {
            e.printStackTrace();
        }
    }  

    private static int findInsertAtIndex(List<JSONObject> linkedList2, int i) throws JSONException {
        int curIndex =0;
        int reqIndex=0;
        for(int j=0;j<linkedList2.size();j++){
            JSONObject jo = (JSONObject) linkedList2.get(j);
            if(jo.getString("type").equalsIgnoreCase("s")){
                if(curIndex==i){
                    reqIndex=j;
                    break;
                }
                curIndex++;
            }
        }
        return reqIndex;
    }

    private static void insertValue(int index, List<JSONObject> linkedList2,double ID,double age,String t) throws JSONException {
        JSONArray ja1= new JSONArray();
        //Copy the data from that index in another JSONArray
        //It is an array, so you will need to do shifting
        for(int i=index;i<linkedList2.size();i++) {
            ja1.put(linkedList2.get(i));
        }
        JSONObject jo  = new JSONObject();
        JSONObject jo3 = new JSONObject();
        jo.put("ID", ID);
        jo.put("Age", age);
        jo3.put("type", t);
        jo3.put("DB", jo);
        linkedList2.add(index, jo3);

        int shiftIndex = index+1;
        for(int i=0;i<ja1.length();i++) {
            linkedList2.add(shiftIndex,(JSONObject) ja1.get(i));
            shiftIndex++;
        }
    }

第一次插入的 O/P

[{"DB":{"ID":1239,"Age":55},"type":"L"}]
For 2nd insertion 
 [{"DB":{"ID":1233,"Age":45},"type":"L"},{"DB":{"ID":1239,"Age":55},"type":"L"},{"DB":{"ID":1239,"Age":55},"type":"L"}]
For 3rd insertion 
[{"DB":{"ID":1233,"Age":45},"type":"L"},{"DB":{"ID":10010,"Age":22},"type":"s"},{"DB":{"ID":1239,"Age":55},"type":"L"},{"DB":{"ID":1239,"Age":55},"type":"L"},{"DB":{"ID":1239,"Age":55},"type":"L"},{"DB":{"ID":1239,"Age":55},"type":"L"}]

Answer 1

在 insertValue() ，首先，将链表元素复制到 json 数组中，然后将新元素添加到链表中，然后再次添加首先复制的元素...这些元素已经在链表中。

一个LinkedList为您处理元素的插入(这就是使用集合的目的)。您不需要移动任何东西或复制自己。

为了说明，在LinkedList<String>上,

// if linkedlist contains ["a", "b", "s"]
linkedlist.add(2, "X");
// linkedlist contains now ["a", "b", "X", "c"]

该方法应该类似于(我还没有编译它):

private static void insertValue(int index, List<JSONObject> linkedList2,
                                double ID, double age, String t) throws JSONException {
    JSONObject jo1  = new JSONObject();
    jo1.put("ID", ID);
    jo1.put("Age", age);
    JSONObject jo2 = new JSONObject();
    jo2.put("type", t);
    jo2.put("DB", jo1);
    linkedList2.add(index, jo2);
}