URL相关的类：

URL;
URLClassLoader;
URLConnection;
URLDecoder;
URLEncoder;
URLStreamHandler;
URLStreamHandlerFactory;
URLSpan;
URLUtil;

GET POST：

GetPostUtils.java

package shortcut.song.com.myapplication;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Map;

/**
 * Created by Administrator on 2017/8/21 0021.
 */

public class GetPostUtils {
    /**
     * 向指定URL 发送GET方式的请求
     * @param url 发送请求的URL
     * @param params 请求参数，请求参数应该是name1=value1&name2=value2的形式
     * @return URL所代表的远程资源的响应
     */

    public static String sendGet(String url, String params) {
        String result = "";
        BufferedReader in = null;
        try {
            String urlName = url + "?"+params;
            URL realUrl = new URL(urlName);
            // 打开和URL之前对应的连接
            URLConnection conn =  realUrl.openConnection();
            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windos NT 5.1; SV1)");
            // 建立实际连接
            conn.connect();
            // 获取所有的响应头字段
            Map<String, List<String>> map = conn.getHeaderFields();
            // 遍历所有的响应头字段
            for (String key: map.keySet()) {
                System.out.println(key +"--->"+ map.get(key));
            }
            // 定义BufferedReader 输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while((line = in.readLine()) != null){
                result += "\n"+line;
            }

        } catch (Exception e) {
            System.out.println("SendGET Exception!!!");
            e.printStackTrace();
        }
        finally {
            try {
                if (in != null) {
                    in.close();
                }
            }catch (IOException e) {
                e.printStackTrace();
            }
        }
        return result;
    }

    /**
     *
     * @param url
     * @param params
     * @return
     */
    public static String sendPost(String url, String params) {
        String result="";
        PrintWriter out = null;
        BufferedReader in = null;

        try {
            URL realUrl = new URL(url);
            // 打开和URL之间的连接
            URLConnection conn = realUrl.openConnection();
            // 设置通用的请求属性
            conn.setRequestProperty("accept", "*/*");
            conn.setRequestProperty("connection", "Keep-Alive");
            conn.setRequestProperty("user-agent",
                    "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
            // 发送POST请求必须设置如下两行
            conn.setDoOutput(true);
            conn.setDoInput(true);

            // 获取URLConnection对象对应的输出流
            out = new PrintWriter(conn.getOutputStream());
            // 发送请求参数
            out.print(params);
            // flush输出缓冲
            out.flush();
            // 定义BufferedReader输入流来读取URL的响应
            in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line;
            while((line = in.readLine()) != null) {
                result += "\n" + line;
            }

        } catch (Exception e){
            System.out.println("Send POST Error!");
            e.printStackTrace();
        }
        finally {
            try {
                if (out != null) {
                    out.close();
                }
                if (in != null) {
                    in.close();
                }
            }catch (IOException ex) {
                ex.printStackTrace();
            }
        }
        return result;
    }

}

AndroidManifest.xml

<uses-permission android:name="android.permission.INTERNET" />

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="shortcut.song.com.myapplication.URLConnectionActivity">

    <Button
        android:id="@+id/btn_get"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="get"/>
    <Button
        android:id="@+id/btn_post"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="post"/>
    <TextView
        android:id="@+id/edt_show"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
</LinearLayout>

package shortcut.song.com.myapplication;

import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class URLConnectionActivity extends AppCompatActivity {

    Button get;
    Button post;
    TextView textView;
    String response;


    Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if (msg.what == 0x123) {
                textView.setText(response);
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_urlconnection);
        get = (Button)findViewById(R.id.btn_get);
        post = (Button)findViewById(R.id.btn_post);
        textView = (TextView)findViewById(R.id.text_show);

        get.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new Thread(){
                    @Override
                    public void run() {
                        super.run();
                        response = GetPostUtils.sendGet("http://192.168.8.27/index.jsp", null);
                        mHandler.sendEmptyMessage(0x123);
                    }
                }.start();
            }
        });

        post.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new Thread(){
                    @Override
                    public void run() {
                        super.run();
                        response = GetPostUtils.sendPost("http://192.168.8.27/index.jsp", "name=song&passwd=123");
                    }
                }.start();
                mHandler.sendEmptyMessage(0x123);
            }
        });
    }
}