How to print key with the help of value in hashmap in android

Question

I want to print key with the help of hashmap. Isee solution these method but i find right solutionif(hashmapOption.containsValue(parent.getItemAtPosition(position).toString())). if this is true than print the key value.

Well you can iterate through all the entries in the map, check whether the value matches and print the key if so. But: a) that's slow; basically HashMap is designed for lookup by key, not value; b) there may be multiple matching values. — Jon Skeet, Nov 18 '15 at 10:18

score 2 · Accepted Answer · edited May 23 '17 at 11:44

You must iterate all entries and print if containing:

// your map is map = HashMap<String, String>
public void printIfContainsValue(Map mp, String value) {
    Iterator it = map.entrySet().iterator();
    while (it.hasNext()) {
        Map.Entry pair = (Map.Entry) it.next();
        // print if found
        if (value.equals(pair.getValue())) {
            System.out.println(pair.getKey() + " = " + pair.getValue());
        }
        it.remove(); // avoids a ConcurrentModificationException
    }
}

Or return the Entry and do what you want with it:

// your map is map = HashMap<String, String>
public Map.Entry containsValue(Map mp, String value) {
    Iterator it = map.entrySet().iterator();
    while (it.hasNext()) {
        Map.Entry pair = (Map.Entry) it.next();
        // return if found
        if (value.equals(pair.getValue())) {
            return pair;
        }
        it.remove(); // avoids a ConcurrentModificationException
    }
    return null;
}

NOTE: as pointed by John Skeet you must know that:

that's slow; basically HashMap is designed for lookup by key, not value;
there may be multiple matching values, this methods will only return first found value.

How to print key with the help of value in hashmap in android

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