Answer by Fathah Rehman P for Java Hashmap: How to get key from value?

public class NewClass1 {    public static void main(String[] args) {       Map<Integer, String> testMap = new HashMap<Integer, String>();        testMap.put(10, "a");        testMap.put(20, "b");        testMap.put(30, "c");        testMap.put(40, "d");        for (Entry<Integer, String> entry : testMap.entrySet()) {            if (entry.getValue().equals("c")) {                System.out.println(entry.getKey());            }        }    }}

Some additional info... May be useful to you

Above method may not be good if your hashmap is really big. If your hashmap contain unique key to unique value mapping, you can maintain one more hashmap that contain mapping from Value to Key.

That is you have to maintain two hashmaps

1. Key to value2. Value to key 

In that case you can use second hashmap to get key.