如何使用Java流和Lambda表达式访问数组中保存的hashmap数据

Question

我在学Java溪流。我有一段使用传统for循环读取HashMap数组的代码:

public void getData() {
    JSONParser objJSONParser = new JSONParser();
    try {
        Object obj = objJSONParser.parse(new FileReader(".\\Resources\\TestData\\LoginTestData.json"));
        JSONObject jsonObj = (JSONObject) obj;
        JSONArray loginCredentialsArray = (JSONArray)jsonObj.get("AdminLogin");     
        
        for(int i=0; i<loginCredentialsArray.size(); i++) 
        {
            JSONObject adminCredentials = (JSONObject)loginCredentialsArray.get(i);
            String username = (String) adminCredentials.get("UserName");
            String password = (String) adminCredentials.get("Password");
            System.out.println("username= " + username);
            System.out.println("password= " + password);
        }
        
    } catch (IOException | ParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        logger.fatal("Exception in 'JSONReader' class: " + e.getMessage());
    }
}

“for”循环的Java流和Lambda代码是什么？

Answer 1

您可以使用IntStream，例如，以这种方式:

IntStream.range(0, loginCredentialsArray.size()).forEach(i -> {
  JSONObject adminCredentials = (JSONObject)loginCredentialsArray.get(i);
  ...
}); 

或者这样说:

IntStream.range(0, loginCredentialsArray.size())
.map(i -> (JSONObject)loginCredentialsArray.get(i))
.forEach(adminCredentials -> {
  String username = (String) adminCredentials.get("UserName");
  String password = (String) adminCredentials.get("Password");
  ...
});