Java HashMap putAll() Method

Example

import java.util.HashMap;
public class Main {
  public static void main(String[] args) {
    HashMap<String, String> capitalCities = new HashMap<String, String>();
    capitalCities.put("England", "London");
    capitalCities.put("Germany", "Berlin");
    capitalCities.put("Norway", "Oslo");
    capitalCities.put("USA", "Washington DC");
    HashMap<String, String> moreCities = new HashMap<String, String>();
    moreCities.put("Canada", "Ottawa");
    moreCities.put("Japan", "Tokyo");
    capitalCities.putAll(moreCities);
    System.out.println(capitalCities);
  }
}