编辑器
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"); System.out.println(capitalCities.keySet()); } }
[USA, Norway, England, Germany]
编辑器