最近看到有个同事在遍历json数组的时候，用for循环写了一层有一层，那么是否有简便的写法呢？当然有了，下面就有用流的行驶，优雅的遍历数组，获取我们想要的数据

public static void main(String[] args) {
    String structure = "[{\"key\":\"111\",\"isRequired\":true,\"isNumber\":true,\"isFixed\":true},{\"key\":\"2\",\"isFixed\":true},{\"key\":\"3\",\"isNumber\":true},{\"key\":\"4\",\"isRequired\":true}]";
    JSONArray jsonArray;

    try {
        jsonArray = JSON.parseArray(structure);
    } catch (JSONException e) {
        System.err.println("Invalid JSON format: " + e.getMessage());
        return;
    }

    List<String> unitList = Optional.ofNullable(jsonArray)
            .orElse(new JSONArray())
            .stream()
            .filter(item -> item instanceof JSONObject)
            .map(item -> {
                JSONObject jsonObject = (JSONObject) item;
                String key = jsonObject.getString("key");
                return key;
            })
            .collect(Collectors.toList());

    System.out.println(unitList);
}