import java.util.HashMap; import java.util.Collections; import java.util.Map; public class Main { public static void main(String[] args) { HashMap<String, String> capitalCities = new HashMap<String, String>(); capitalCities.put("England", "London"); Map<String, String> readOnly = Collections.unmodifiableMap(capitalCities); try { readOnly.put("Germany", "Berlin"); } catch (UnsupportedOperationException e) { System.out.println("Error: the map cannot be changed."); } } }