java URL的简单使用

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;

public static String sendGet(String url, Map<String, String> param) {
    String paramStr = getParam(param);
    String result = "";
    BufferedReader in = null;
    try {
        String urlNameString = url + "?" + paramStr;
        URL realUrl = new URL(urlNameString);
        // 打开和URL之间的连接
        URLConnection connection = realUrl.openConnection();
        // 设置通用的请求属性
        connection.setRequestProperty("accept", "*/*");
        connection.setRequestProperty("connection", "Keep-Alive");
        connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
        connection.setRequestProperty("Accept-Charset", "utf-8");
        connection.setRequestProperty("contentType", "utf-8");
        // 建立实际的连接
        connection.connect();
        // 获取所有响应头字段
        // Map<String, List<String>> map = connection.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(connection.getInputStream(), "utf-8"));
        String line;
        while ((line = in.readLine()) != null) {
            result += line;
        }
    } catch (Exception e) {
        System.out.println("发送GET请求出现异常！" + e);
        e.printStackTrace();
    }
    // 使用finally块来关闭输入流
    finally {
        try {
            if (in != null) {
                in.close();
            }
        } catch (Exception e2) {
            e2.printStackTrace();
        }
    }
    return result;
}