Question

I’m new to Java. I implemented a Hash Map as shown below.
In a particular scenario I wanted to retrieve the key using values of the key.
For Eg: If user enters “Dravid”, then I need to retrieve “2” from the Hash Map.

And I want to use only one hash map to implement this.

Can anyone help me with this?

HashMap<String,String> streetno=new HashMap<String,String>();
    streetno.put("1", "Sachin");
    streetno.put("2", "Dravid");
    streetno.put("3","Sehwag");
    streetno.put("4", "Laxman");
    streetno.put("5", "Kohli");

Answer 1

To do this, you would need to use a bi-directional hashmap. Consider using the Apache Commons implementation.

Without it, you’d need to iterate over all the key / value pairs in the map and test for when the value equals “Dravid”, then return the key. Like so:

for (Entry<String, String> pair : streetno.entrySet()) {
      if (pair.getValue().equals("Dravid")) {
        System.out.println("Found Dravid at key: " + pair.getKey());
      }
    }