java - 展平嵌套的Map，其中包含未知级别的嵌套数组，并且递归地映射

你可以使用递归来展平Map。每次遇到a时Map，通过展平来递归Map; 当你遇到时List，请对其进行迭代，然后将索引添加到当前键中。否则，可以简单地设置一个值。请参阅此处的以下代码。

public static Map<String, Object> flatten(final Map<String, Object> map) {
    return flatten("", map, new HashMap<>());
    //use new TreeMap<>() to order map based on key
}

@SuppressWarnings("unchecked")//recursive helper method
private static Map<String, Object> flatten(final String key, final Map<String, Object> map,
        final Map<String, Object> result) {
    final Set<Map.Entry<String, Object>> entries = map.entrySet();
    if (!entries.isEmpty()) {
        for (final Map.Entry<String, Object> entry : entries) {
            //iterate over entries
            final String currKey = key + (key.isEmpty() ? "" : '.') + entry.getKey();
           //append current key to previous key, adding a dot if the previous key was not an empty String
            final Object value = entry.getValue();
            if (value instanceof Map) {//current value is a Map
                flatten(currKey, (Map<String, Object>) value, result);//flatten Map
            } else if (value instanceof List) {//current value is a List
                final List<Object> list = (List<Object>) value;
                for (int i = 0, size = list.size(); i < size; i++) {
                    result.put(currKey + '.' + (i + 1), list.get(i));
                }
                //iterate over the List and append the index to the current key when setting value
            } else {
                result.put(currKey, value);//set normal value
            }
        }
    }
    return result;
}
public static void main(final String[] args){
    final Map<String, Object> flattened = flatten(dates);
    System.out.println(flattened);
}