MultiValueMap in java

Question

I'm studying with Hashmap with Multiple parameters(1 key, 2 values) and i was able to find apache multiValueMap for my issue.

Here is my codes for multiValueMap.

import java.util.Set;
import org.apache.commons.collections.map.MultiValueMap;
import org.apache.commons.collections.MultiMap;

public class multiValueMap {

public static void main(String args[]) {
   String a, b, c;
   MultiMap mMap = new MultiValueMap();

   mMap.put("a", "Hello there, It's a wonderful day");
   mMap.put("a", "nice to meet you");

   Set<String> keys = mMap.keySet();

   for (String key : keys) {
      System.out.println("Key = " + key);
      System.out.println("Values = " + mMap.get(key));
      a = String.valueOf(mMap.get(key));

      System.out.println("A : " + a);
    }
 }
}
// The result as below
 Key = a 
 Value = [Hello there, It's a wonderful day, nice to meet you]
 A : [Hello there, It's a wonderful day, nice to meet you]

Here is my question how can I store first value for string b, and second for c? if I substring the MultiMap values depends on "," then it would stores Hello there only. please give me helpful your advices.

Solution 1

You can try following :

String a, b, c;

MultiMap mMap = new MultiValueMap();
mMap.put("a", "Hello there, It's a wonderful day");
mMap.put("a", "nice to meet you");

Set<String> keys = mMap.keySet();

for (String key : keys) {
    System.out.println("Key = " + key);
    System.out.println("Values = " + mMap.get(key));
    List<String> list = (List<String>) mMap.get(key);

    b = list.get(0);
    c = list.get(1);
    System.out.println("B : " + b);
    System.out.println("C : " + c);
} 

Solution 2

You don't have to do a split. This is the documentation of MultiMap that is found:

MultiMap mhm = new MultiHashMap();
 mhm.put(key, "A");
 mhm.put(key, "B");
 mhm.put(key, "C");
 Collection coll = (Collection) mhm.get(key);

Now when you do a get() call on a multimap, it gives you a collection. The first item will be your b and the second one will be your c.

Solution 3

You can also use a key and object to store multiple values in Multimap. Something like this, MultiValueMap mv = new LinkedMultiValueMap<~>();

Comments

[user3810857]

Seems like it needs more details. actually, I want to store numerous data(more than 1000) from DB and it covers 3 parameters(data no(int), channel id(int), description(String)). but If I store them to Hashmap(Key, Value) It's not enough for 3 paramets hence, I decided to use MultiValueMap. 2 answers above does not fully solve my issue.