Java tutorial
import java.util.HashMap; import java.util.Map; public class Main { public static void main(String[] a) { Map<String, String> map = new HashMap<String, String>(); map.put("key1", "value1"); map.put("key2", "value2"); map.put("key3", "value3"); map.put(null, null); Map<String, String> map2 = new HashMap<String, String>(); map2.put("key4", "value4"); map2.put("key5", "value5"); map2.put("key6", "value6"); map.putAll(map2); System.out.println(map); } }