Adding List of JSONArray value into List of List and Put List of List One by one Map

Question

1st Step : adding value[x,y,z] into the List roles. Then Put key and roles(value) into KV(HashMap).

|
|___>>>>{a=[x, y, z]}

2nd Step: adding value[x,z] into the roles List its added to the List successfully but while adding it into roles it changes the value[x,y,z] to value[x,z] in 1st Step.

|
|_____>>>>{a=[x, z], b=[x, z]}

Expected: {a=[x, y, z],b=[x, z]}

3nd Step: adding value[x,y,z] into the roles List its added to the List successfully but while adding it into roles it changes the value[x,z] to value[x,y,z] in 2st Step and for that changed in 1st step during performing 2nd step.

|
|______>>>>{a=[x, y, z], b=[x, y, z], c=[x, y, z]}

Expected: {a=[x, y, z],b=[x, z],c=[x, y, z]}

Please help me with this code, why its Changing the Values that I previously added to Map.

"json":{
"a": [
  "x",
  "y",
  "z"
],
"b": [
  "x",
  "z"
],
"c": [
  "x",
  "y",
  "z"
],
"d": [
  "y",
  "z"
]
}

public Map<String,List<String>> getUserDetails(String json) throws IOException
{
    Map<String,List<String>> **KV** = new HashMap<>();
    List<String> **roles** = new LinkedList<>();


    List<String> arrayKeys = jsonUtil.getJsonArrayKey(json);
    System.out.println("Array Key      :  " + arrayKeys);
    for (String **key** : arrayKeys)
    {
        roles.clear();
        JSONObject jsonObject = new JSONObject(json);
        JSONArray explrObject = jsonObject.getJSONArray(key);
        for (int i = 0; i < explrObject.length(); i++)
        {
            String value = (explrObject.get(i).toString());
            System.out.println("Array Value : " + value);
            **roles**.add(value);
        }
         **KV**.put(**key**,**roles**);
        System.out.println("Key and Value     :"+KV);
    }
    return profileOrg_KV;
}

Actual OutPut:

Array Key      :  [a, b, c, d]

Array Value : x
Array Value : y
Array Value : z
Key and Value      :{a=[x, y, z]}

Array Value : x
Array Value : z
Key and Value      :{a=[x, z], b=[x, z]}

Array Value : x
Array Value :y
Array Value : z
Key and Value      :{a=[x, y, z], b=[x, y, z], c=[x, y, z]}

Array Value : y
Array Value : z
Key and Value     :{a=[x, y, z], b=[x, y, z], c=[y , z], d=[x, y, z]}

Expected OutPut:

Array Key      :  [a, b, c, d]

Array Value : x
Array Value : y
Array Value : z
Key and Value      :{a=[x, y, z]}

Array Value : x
Array Value : z
Key and Value      :{a=x, y, z], b=[x, z]}

Array Value : x
Array Value :y
Array Value : z
Key and Value      :{a=[x, y, z], b=[x, z], c=[x, y, z]}

Array Value : y
Array Value : z
Key and Value     :{a=[x, y, z], b=[x, z], c=[y , z], d=[x, z]}

Alexander Ivanchenko · Accepted Answer · 2022-12-01 19:39:55Z

You're associating the same the list roles with every Key in your Map (because you're using a reference to the same object, and invoking clean() on the list only removes all its contents it doesn't allocate a new list as you might be expected).

You need to instantiate a new list with each iteration step, so that every Key would be mapped to its own List which is not shared with other Keys.

public Map<String, List<String>> getUserDetails(String json) throws IOException {
    Map<String, List<String>> rolesByKey = new HashMap<>();
    
    List<String> arrayKeys = jsonUtil.getJsonArrayKey(json);
    
    for (String key : arrayKeys) {
        List<String> roles = new LinkedList<>();
        JSONObject jsonObject = new JSONObject(json);
        JSONArray explrObject = jsonObject.getJSONArray(key);
        for (var role : explrObject) {
            roles.add(role.toString());
        }
        rolesByKey.put(key, roles);
    }
    return rolesByKey;
}

Sidenote: please, get familiar and try to adhere to the Java language naming conventions.

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