I have a method that takes in a List<String> and List<Map<String, Object>>:
public List<Map<String, Object>> filterMethod() {
List<String> listId = this.getUserIds(); //includes only the user id's
List<Map<String, Object>> listUser = this.getUserDetails(); // includes user_id, user_name, and user_email
List<Map<String, Object>> filteredListUser = null;
return filteredListUser;
}
What I would like to be able to do, is compare these two and return a new List<Map<String, Object>>.
The comparison I'd like to do shown as an example:
Let's say:
List<String> listId =
[
"8000",
"8002",
"8004",
"8006",
"8010",
"8012",
"8014",
"8016",
"8018",
"8020",
"8022",
"8024"
]
List<Map<String, Object>> listUser =
[
{
"USER_ID": "8001",
"USER_NAME": "username1",
"USER_MAIL": "[email protected]"
},
{
"USER_ID": "8002",
"USER_NAME": "username2",
"USER_MAIL": "[email protected]"
},
{
"USER_ID": "8003",
"USER_NAME": "username3",
"USER_MAIL": "[email protected]"
},
{
"USER_ID": "8004",
"USER_NAME": "username4",
"USER_MAIL": "[email protected]"
},
{
"USER_ID": "8005",
"USER_NAME": "username5",
"USER_MAIL": "[email protected]"
},
{
"USER_ID": "8006",
"USER_NAME": "username6",
"USER_MAIL": "[email protected]"
},
{
"USER_ID": "8007",
"USER_NAME": "username7",
"USER_MAIL": "[email protected]"
}
]
I would like to return a new filtered List<Map<String, Object>>, that contains listUser rows where a listUser USER_ID is in listId (i.e:)
List<Map<String, Object>> filteredListUser =
[
{
"USER_ID": "8002",
"USER_NAME": "username2",
"USER_MAIL": "[email protected]"
},
{
"USER_ID": "8004",
"USER_NAME": "username4",
"USER_MAIL": "[email protected]"
},
{
"USER_ID": "8006",
"USER_NAME": "username6",
"USER_MAIL": "[email protected]"
}
]
The issue comes when I need to compare the user_id from listUser with listId in order to check if I need to add the row to filteredListUser.
I would know how to do this if this were simply two string arrays like so:
String[] a = {1, 2, 3, 4, 5, 6, 7};
String[] b = {2, 4, 6, 8, 10};
ArrayList<String> c = new ArrayList<String>();
for (int i = 0; i < a.length; i++) {
if (Arrays.asList(b).contains(a[i])) {
c.add(a[i]);
}
}
I think a for-loop would also be appropriate for the List comparisons, but I am unsure as to how I can compare the user_id in listUser with listId in List<Map<String, Object>> and List<String>.
As an attempt and pseudo-code perspective, what I am trying to accomplish is this:
public List<Map<String, Object>> filterMethod() {
List<String> listId = this.getUserIds(); //includes only the user id's
List<Map<String, Object>> listUser = this.getUserDetails(); // includes user_id, user_name, and user_email
List<Map<String, Object>> filteredListUser = null;
for (int i = 0; i < listUser.length; i++) {
if (listId.contains(listUser.USER_ID[i])) {
filteredListUser.add(listUser[i]);
}
}
return filteredListUser;
}
I'm not entirely sure where to go from here however - would appreciate any help!
Apologies if this is a really rudimentary question - I'm very new to programming. Thank you in advance!
I would iterate the List<Map<String, Object>> and check corresponding value to USER_ID is present in List<String> listId. below is the approach by using java-8 streams
List<Map<String, Object>> result = listUser.stream()
.filter(m-> listId.contains(m.get("USER_ID")))
.collect(Collectors.toList());
or By using simple for loop
List<Map<String, Object>> filteredListUser = new ArrayList<>();
for(Map<String, Object> m : listUser) {
if(listId.contains(m.get("USER_ID"))) {
filteredListUser.add(m);
}
}
You can also do it by using removeIf but this modifies the existing map
listUser.removeIf(m->!listId.contains(m.get("USER_ID")));