Map HashMap 获取Key值的方法

List<Map<String, Fragment>> mDatas = new ArrayList<>();

    Map<String, Fragment> map1 = new ArrayMap<>();
    map1.put("首页", OneFragment.newInstance());

    Map<String, Fragment> map2 = new ArrayMap<>();
    map2.put("闪贷大全", TwoFragment.newInstance());

    Map<String, Fragment> map3 = new ArrayMap<>();
    map3.put("个人中心", ThreeFragment.newInstance());

    mDatas.add(map1);
    mDatas.add(map2);
    mDatas.add(map3);



Iterator<String> iterator = mDatas.get(position).keySet().iterator();
iterator.next()  //Key
mDatas.get(position).get(iterator.next())  //Value

方法1：keySet()

Map<Character, Integer> map = new HashMap<>();

for (char key : map.keySet()) {
    res += key + "" + map.get(key);
}
System.out.println(res);

Iterator<Character> iterator11 = map.keySet().iterator();
while (iterator11.hasNext()) {
    Character key = iterator11.next();
    res += key + "" + map.get(key);
}
System.out.println(res);

方法2：entrySet() 效率高

for (Map.Entry<Character, Integer> entry : map.entrySet()) {
    res += entry.getKey() + "" + entry.getValue();
}
System.out.println(res);

Iterator<Map.Entry<Character, Integer>> iterator2 = map.entrySet().iterator();
while (iterator2.hasNext()) {
    Map.Entry<Character, Integer> entry = iterator2.next();
    res += entry.getKey() + "" + entry.getValue();
}
System.out.println(res);