HashMap – Get value from key example

Description

Program to get value from HashMap when the key is provided.

Example

import java.util.HashMap;
class HashMapDemo{ 
  public static void main(String[] args) {
     // Create a HashMap
     HashMap<Integer, String> hmap = new HashMap<Integer, String>();
 
     //add elements to HashMap
     hmap.put(1, "AA");
     hmap.put(2, "BB");
     hmap.put(3, "CC");
     hmap.put(4, "DD");
 
     // Getting values from HashMap
     String val=hmap.get(4);
     System.out.println("The Value mapped to Key 4 is:"+ val);
 
     /* Here Key "5" is not mapped to any value so this 
      * operation returns null.
      */
     String val2=hmap.get(5);
     System.out.println("The Value mapped to Key 5 is:"+ val2);
  }
}

Output:

The Value mapped to Key 4 is:DD
The Value mapped to Key 5 is:null

Note: In the above program the key 5 is not mapped to any value so the get() method returned null, However you must not use this method for checking existence of a Key in HashMap because a return value of null does not necessarily indicate that the map contains no mapping for the key; it’s also possible that the map explicitly maps the key to null. You must use the containsKey() method for checking the existence of a Key in HashMap.