Java 周遊HashMap的兩種方式

（1）keySet方法：将HashMap中鍵傳回并使用set集合存儲。

public Set<K> keySet()
           

案例

private static void show01() {
        Map<String, String> stringStringHashMap = new HashMap<>();
        stringStringHashMap.put("aa","aaa");
        stringStringHashMap.put("bb","bbb");
        
        Set<String> set = stringStringHashMap.keySet();
        for (String str : set) {
            System.out.println(stringStringHashMap.get(str));
        }


    }
           

（2）entrySet方法：将map中存儲的鍵值對傳回到entry對象中，并用set集合存儲

public Set<Map.Entry<K,V>> entrySet()
           

案例：

private static void show01() {
        Map<String, String> stringStringHashMap = new HashMap<>();
        stringStringHashMap.put("aa","aaa");
        stringStringHashMap.put("bb","bbb");
        Set<Map.Entry<String, String>> entries = stringStringHashMap.entrySet();
        Iterator<Map.Entry<String, String>> iterator =
                entries.iterator();
        while(iterator.hasNext()){
            System.out.println(iterator.next().getKey());
        }
}