## 实例 ~~~ Map<String, String> m1 = new HashMap<>(); m1.put("张三", "18"); m1.put("李四", "20"); m1.put("王五", "16"); Map<String, String> m2 = new HashMap<>(); m2.put("jack", "18"); m2.put("richard", "20"); m2.put("milan", "16"); Map<String, String> m3 = new HashMap<>(); m3.put("超人", "18"); m3.put("钢铁侠", "20"); m3.put("蜘蛛侠", "16"); Map<String, Map<String, String>> m = new HashMap<>(); m.put("java", m1); m.put("php", m2); m.put("c++", m3); Set<Map.Entry<String, Map<String, String>>> entry = m.entrySet(); Iterator<Map.Entry<String, Map<String, String>>> iterator = entry.iterator(); while (iterator.hasNext()) { Map.Entry<String, Map<String, String>> mapEntry = iterator.next(); String key = mapEntry.getKey(); Map<String, String> value = mapEntry.getValue(); Set<String> keys = value.keySet(); for (String str : keys) { System.out.println((str + ":" + m.get(key).get(str))); } } ~~~