Unordered Data using HashMap in Java

May 1, 2017
Categorised in: Java Core
Understanding through Code
import java.util.HashMap; import java.util.Map; public class HashMapDemo { public static void main( String[] args ){ Map<String, String> map = new HashMap<>(); map.put("India", "First"); map.put("US", "Second"); map.put("Canada", "Third"); System.out.println(map); map.put("Russia", "Fourth"); System.out.println(map); String mapString = map.get("US"); System.out.println("The US stands at: " +mapString); System.out.println(mapString); map.remove("Russia"); } }
Output
- {Canada=Third, US=Second, India=First}
- {Canada=Third, US=Second, India=First, Russia=Fourth}
- The US stands at: Second
- Second
Notes
- HashMap is unordered data collection.
- HashMap is implementation of Map. Just like ArrayList is an implementation of List.
- Maps are in Key, Value pairs.
- You can look up an item in HashMap with the help of Key.