HashMap Example

Map is an Interface and which is available in java.util package and HashMap is an implementation of the Map interface. HashMap stores the data in key/value pair.

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

public class HashMapExample {

    public static void main(String[] args) {

        Map<Object, Object> map = new HashMap<Object, Object>();
        // put the key and values in String format
        map.put("1", "Java");
        map.put("2", "Programming in C");
        map.put("AI", "Lisp");
        map.put("Script", "JavaScript");

        System.out.println("Before Change - " + map.get("1"));
        System.out.println("Key \t Value");
        System.out.println("----------------");

        // loop through the map data using Iterator Interface
        Iterator<?> iterator = map.entrySet().iterator();
        Map.Entry<String, String> entry = null;
        while (iterator.hasNext()) {
            entry = (Entry<String, String>) iterator.next();
            System.out.println(entry.getKey() + "\t" + entry.getValue());
        }

        // Let's change the value for the key 1 and key 2
        map.put("1", "OOP");
        map.put("2", "Procedural");
        System.out.println("After Change - " + map.get("1"));
        System.out.println("After Change - " + map.get("2"));
    }
}

Output: