# 用Native Java call Rest API
今天的Hackerrank考題真的花太多時間了，來不及寫完，後來用Eclipse重頭思考一次花了一個半小時才寫完，
以後有上機考的題目還是要先用Eclipse親自跑過一次才比較準確。

package practice.java8;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import javax.net.ssl.HttpsURLConnection;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;

import org.springframework.http.HttpMethod;

public class Test {

    public static void main(String[] args) {
        getUsernames(10);
    }

    public static List<String> getUsernames(int threshold){
        List<String> resultList = new ArrayList<>();
        String urlStr = "https://jsonmock.hackerrank.com/api/article_users/search?page=2";
        try {
            URL url = new URL(urlStr);
            HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
            
            conn.setRequestMethod(HttpMethod.GET.toString());
            conn.setRequestProperty("Content-Type", "application/json");
            
            if(conn.getResponseCode() == HttpsURLConnection.HTTP_OK) {
                BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                StringBuffer response = new StringBuffer();
                String inputline = null;
                
                while((inputline = in.readLine()) != null) {
                    response.append(inputline);
                }
                in.close();
                
                String responseStr = response.toString();
                
                System.out.println("responseStr: "+responseStr);
                
                Map resultMap = jsonStringToMap(responseStr);
                List<Map<Object,Object>> dataList =  (List<Map<Object, Object>>) resultMap.get("data");
                
                
                for(Map<Object,Object> data:dataList) {
                    if((Integer )data.get("submission_count") > threshold) {
                        resultList.add((String) data.get("username"));
                    }
                }
                
                System.out.println(resultList);
                
            }else {
                System.out.println("ERROR: statusCode: "+conn.getResponseCode());
            }
        } catch (Exception e) {
            System.out.println("ERROR: "+e);
        }
        
        return resultList;
    }
    
    public static Map jsonStringToMap(String jsonStr)  throws Exception{
        ScriptEngineManager sem = new ScriptEngineManager();
        ScriptEngine engine = sem.getEngineByName("javascript");
        String script = "Java.asJSONCompatible("+jsonStr+")";
        Object result = engine.eval(script);
        Map content = (Map) result;
        
        return content;
    }
}

###### tags: `Java`