CODEWITHSUNDEEP
javaandroidoptimizationperformancehashmap
Blundell
Blundell

Reputation: 76458

Merge two Hash Maps Android

I want to merge Two HashMaps.

I could use map1.putAll(map2); but I don't want to overwrite the key's as yes they will have conflicting keys.

So the keys in each map will be like this

word1     word1
word2     word2
word3     word3

and when I merge them I would like:

word1
word2
word3
word4
word5
word6

It can just overwrite the keys, aslong as the keys are incremental and use the first key text i.e. reads one of the pairs and extracts 'word' so each would be word1 word2.

But the other caveat I was thinking of the mobile environment and what I can do without having to put up a loading screen or even capable of.

So as a starter I suppose:

    HashMap<String, Object> hm1 = new HashMap<String, Object>();
    hm1.put("key1", "a");
    hm1.put("key2", "a");
    hm1.put("key3", "a");
    HashMap<String, Object> hm2 = new HashMap<String, Object>();
    hm2.put("key1", "1");
    hm2.put("key2", "2");
    hm2.put("key3", "3");

    HashMap<String, Object> newHM = new HashMap<String, Object>();      
    String keyWord = "";
    for (String  s: hm1.keySet()) {
        keyWord = s;
        break;
    }
    int count = 0;
    for (Object o : hm1.values()) {
        newHM.put(keyWord+count, o);
    }
    for (Object o : hm2.values()) {
        newHM.put(keyWord+count, o);
    }

But I'm wondering, how efficient is this? It looks correct, And is there a better way to do it? I don't want to use extra object's unnecessarily

Upvotes: 3

Views: 4067

Answers (2)

Blundell
Blundell

Reputation: 76458

To match my example it would be:

@Override
public void putAll(Map<? extends String, ? extends Object> m) {
    for (Map.Entry<? extends String, ? extends Object> entry : m.entrySet()) {
        String keyWord = "";
        for (String  s: this.keySet()) {
          keyWord = s.substring(0, s.length()-1);
          break;
        }
        int i = 0;
        while (this.containsKey(i)) {
            i++;
        }
        this.put(keyWord +i, entry.getValue());
    }
}

Upvotes: 0

Colin Hebert
Colin Hebert

Reputation: 93167

If your keys are incremental an basically represent a simple index, you should use a List.

You could try your own implementation of List which will also store a keyword.

class KeyWordedArrayList<T> extends ArrayList<T>{
    private final String keyword;

    public KeyWordedArrayList(String keyword){
        this.keyword = keyword;
    }

    public String getKeyword(){
        return keyword;
    }
}

You can also do an implementation of Map :

class KeyWordedMap<T> extends HashMap<Integer, T> {
    private final String keyword;

    public KeyWordedMap(String keyword) {
        this.keyword = keyword;
    }

    public String getKeyword() {
        return keyword;
    }

    @Override
    public void putAll(Map<? extends Integer, ? extends T> m) {
        for (Map.Entry<? extends Integer, ? extends T> entry : m.entrySet()) {
            int i = entry.getKey();
            while (this.containsKey(i)) {
                i++;
            }
            this.put(i, entry.getValue());
        }
    }
}

Upvotes: 2

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