无法在java中连接REST api

我正在尝试从下面的RESTAPI获得响应。当我在浏览器中打开该URL时，我从服务器获取xml代表。但当我试图使用java程序获得相同的结果时，我得到了下面的异常

IOEXCeption
java.net.UnknownHostException: rxnav.nlm.nih.gov
    at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
    at java.net.PlainSocketImpl.connect(Unknown Source)
    at java.net.SocksSocketImpl.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at java.net.Socket.connect(Unknown Source)
    at sun.net.NetworkClient.doConnect(Unknown Source)
    at sun.net.www.http.HttpClient.openServer(Unknown Source)
    at sun.net.www.http.HttpClient.openServer(Unknown Source)
    at sun.net.www.http.HttpClient.<init>(Unknown Source)
    at sun.net.www.http.HttpClient.New(Unknown Source)
    at sun.net.www.http.HttpClient.New(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
    at java.net.HttpURLConnection.getResponseCode(Unknown Source)
    at com.test.demo.RestConnector.run(RestConnector.java:22)
    at java.lang.Thread.run(Unknown Source)

1） 错误清楚地表明“无法解析主机名”

2） 问：您的AndroidManifest.xml是否授予Internet权限？确保它包含以下行：

3） 问：这是真的设备还是模拟器？如果是后者，考虑重新创建你的AVD。信不信由你，这有时会有所帮助

4） 最后，以下是一些可能有帮助的其他提示（包括代理服务器配置）：

---

尝试处理asynctask..您好，谢谢您的回复。但这是我正在运行的简单java程序。它不是特定于android的

import java.io.BufferedReader; 
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class RestConnector implements Runnable{

    @Override
    public void run() {
        String URLString = "http://rxnav.nlm.nih.gov/REST/classes?src=MESH";

        try {
            URL url = new URL(URLString);
            HttpURLConnection connection  =  (HttpURLConnection)url.openConnection();

            connection.setRequestMethod("GET");
            connection.setRequestProperty("Accept", "application/xml");
            if(connection.getResponseCode() != 200){
                System.out.println("Failed to connect:"+connection.getResponseCode());
                System.out.println("Response Message:"+connection.getResponseMessage());
            }

            System.out.println("I am here ");
            BufferedReader  reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));

            String line ; 
            while((line = reader.readLine()) != null){
                System.out.println(line);
            }

            connection.disconnect();

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            System.out.println("IOEXCeption");
            e.printStackTrace();
        }

    }

    public static void main(String[] args) {

        Thread t = new Thread(new RestConnector());
        t.start();


    }


}