Java：从嵌套HashMap获取数据

Question

Hi Folks i have looked at below mention question for answer but it was not helpful as they give answer for static value while i need to get value from dynamic approch

How to put/get values into/from Nested HashMap

Getting value from Nested HashMap into another Map

How do I access nested HashMaps in Java?

This is my Scenario :

This is my class for adding and retrieving data from HashMap :-

HashMap<Integer, String> xmlQueryNode = new HashMap<Integer, String>();
HashMap<Integer, HashMap<Integer, String>> splunkHashMap = new HashMap<Integer, HashMap<Integer, String>>();
id = 0;
xmlQueryNode.put(0, "F0name");
xmlQueryNode.put(1, "L0name");
xmlQueryNode.put(2, "M0name");

splunkHashMap.put(id, xmlQueryNode);

id = 1;
xmlQueryNode.put(0, "F1name");
xmlQueryNode.put(1, "L1name");
xmlQueryNode.put(2, "M1name");

splunkHashMap.put(id, xmlQueryNode);

id = 2;
xmlQueryNode.put(0, "F2name");
xmlQueryNode.put(1, "L2name");
xmlQueryNode.put(2, "M2name");

splunkHashMap.put(id, xmlQueryNode);

id = 3;
xmlQueryNode.put(0, "F3name");
xmlQueryNode.put(1, "L3name");
xmlQueryNode.put(2, "M3name");

splunkHashMap.put(id, xmlQueryNode);

for (Integer key : splunkHashMap.keySet()) {
    HashMap<Integer, String> temp =  new HashMap<Integer, String>();
    //System.out.println(key);
    temp = otsdbQueryData.get(key);
    for(Integer key1: temp.keySet()){
        System.out.println(temp.get(key1));
    }
}

Problem with this code is that i get below output for all 4 entries :-

F3name
L3name
M3name

F3name
L3name
M3name

F3name
L3name
M3name

F3name
L3name
M3name

Can anyone point me where i am making mistake because My hashmaps are being overwritten by last inserted hashmap??

Answer 1

after put inner hashmap you need to reinitialise that map.

xmlQueryNode = new HashMap<Integer,String>();
xmlQueryNode.put(0, "F1name");
xmlQueryNode.put(1, "L1name");
xmlQueryNode.put(2, "M1name");

otherwise it will update the same reference.

Please check the updated code.

int id =0;

HashMap<Integer, String> xmlQueryNode = new HashMap<Integer, String>();
HashMap<Integer, HashMap<Integer, String>> splunkHashMap = new HashMap<Integer, HashMap<Integer, String>>();
id = 0;
xmlQueryNode.put(0, "F0name");
xmlQueryNode.put(1, "L0name");
xmlQueryNode.put(2, "M0name");

splunkHashMap.put(id, xmlQueryNode);

xmlQueryNode = new HashMap<Integer, String>();
id = 1;
xmlQueryNode.put(0, "F1name");
xmlQueryNode.put(1, "L1name");
xmlQueryNode.put(2, "M1name");

splunkHashMap.put(id, xmlQueryNode);

xmlQueryNode = new HashMap<Integer, String>();
id = 2;
xmlQueryNode.put(0, "F2name");
xmlQueryNode.put(1, "L2name");
xmlQueryNode.put(2, "M2name");

splunkHashMap.put(id, xmlQueryNode);

xmlQueryNode = new HashMap<Integer, String>();
id = 3;
xmlQueryNode.put(0, "F3name");
xmlQueryNode.put(1, "L3name");
xmlQueryNode.put(2, "M3name");

splunkHashMap.put(id, xmlQueryNode);

for (Integer key : splunkHashMap.keySet()) {
    HashMap<Integer, String> temp =  new HashMap<Integer, String>();
    //System.out.println(key);
    temp = splunkHashMap.get(key);
    for(Integer key1: temp.keySet()){
        System.out.println(temp.get(key1));
    }
}

Answer 2

xmlQueryNode reference is getting overwritten again and again. Check below code.

HashMap<Integer, String> xmlQueryNode = new HashMap<Integer, String>();
HashMap<Integer, HashMap<Integer, String>> splunkHashMap = new HashMap<Integer, HashMap<Integer, String>>();
id = 0;
xmlQueryNode.put(0, "F0name");
xmlQueryNode.put(1, "L0name");
xmlQueryNode.put(2, "M0name");

splunkHashMap.put(id, xmlQueryNode);

id = 1;
xmlQueryNode = new HashMap<Integer,String>();
xmlQueryNode.put(0, "F1name");
xmlQueryNode.put(1, "L1name");
xmlQueryNode.put(2, "M1name");

splunkHashMap.put(id, xmlQueryNode);

id = 2;
xmlQueryNode = new HashMap<Integer,String>();
xmlQueryNode.put(0, "F2name");
xmlQueryNode.put(1, "L2name");
xmlQueryNode.put(2, "M2name");

splunkHashMap.put(id, xmlQueryNode);

id = 3;
xmlQueryNode = new HashMap<Integer,String>();
xmlQueryNode.put(0, "F3name");
xmlQueryNode.put(1, "L3name");
xmlQueryNode.put(2, "M3name");

splunkHashMap.put(id, xmlQueryNode);

for (Integer key : splunkHashMap.keySet()) {
    HashMap<Integer, String> temp =  new HashMap<Integer, String>();
    //System.out.println(key);
    temp = otsdbQueryData.get(key);
    for(Integer key1: temp.keySet()){
        System.out.println(temp.get(key1));
    }
}