CODEWITHSUNDEEP
androidhashmap
Looking Forward
Looking Forward

Reputation: 3585

Getting only one value of single key in android

In my android app, I'm trying to get all values of single key using hash map. Below is my code. but I am getting only one value "maharashtra" for key "blr" and not "banglore" (in my code). What am I missing?

    HashMap<String, String> myMap = new HashMap<String, String>();
    myMap.put("ind", "india");
    myMap.put("tn", "tamilnadu" + " How");

    myMap.put("blr","bangalore");
     myMap.put("blr","maharashtra");
    Set<Entry<String,String>> set = myMap.entrySet();

    for (Map.Entry<String, String> me : set) {
        if(me.getKey().equals("blr")){
            System.out.println(me.getValue());

    }

}

Upvotes: 0

Views: 1485

Answers (5)

Looking Forward
Looking Forward

Reputation: 3585

Finally got solution. Awesom...

import java.util.HashMap;
import java.util.Map;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.ArrayList;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;


public class hashmap {

    /**
     * @param args
     */
    public static void main(String[] args) {
       // HashMap<String, List<String> > myMap = new HashMap<String, List<String> >();
      Map<String,List<String>> myMap = new HashMap<String,List<String>>();

        List<String> arr4 = new ArrayList<String>();
        arr4.add("india");
        arr4.add("tamilnadu");
        arr4.add("tamilnadu");
        arr4.add("tamilnadu");
        arr4.add("tamilnadu");

        myMap.put("tn", arr4);
        Set<Entry<String,List<String>>> set = myMap.entrySet();

        for (Map.Entry<String, List<String>> me : set) {
            if(me.getKey().equals("tn")){
                System.out.println(me.getValue());

        }

    }

}
}

Upvotes: 1

spin.goran
spin.goran

Reputation: 416

Probably you should use HashMap<String, List<String>> instead of HashMap<String, String>. To add element to map :

yMap.put("blr", new ArrayList<String>());
yMap.get("blr").add("maharashtra");

Upvotes: 0

user1162766
user1162766

Reputation:

First of all: you can't. As stated here:

public V put(K key, V value)

Associates the specified value with the specified key in this map. If the map previously contained a mapping for the key, the old value is replaced.

Please read: http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html

Second: If you are using a Key, Value structure you most likely shouldn't think of ever having duplicate keys, it defeats the purpose of a Key, Value collection.

A simple solution would be to use HashMap<String, List<String>> instead of HashMap<String, String>. Storing all the values in the List<String>.

Upvotes: 3

bofredo
bofredo

Reputation: 2348

the keys are unique. so you are simply just overwriting the first assignment 

myMap.put("blr","bangalore");

with

myMap.put("blr","maharashtra");

so, use another key!?

Upvotes: 0

Ivo
Ivo

Reputation: 23164

the point of a hashmap is that keys are unique. so you are overwriting bangalore with maharashtra with myMap.put("blr","maharashtra");

Upvotes: 0

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