URLConnection获取网页的数据

package com.strr.connection;

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.nio.charset.StandardCharsets;
import java.util.Base64;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

public class URLConnectionTest {
    public static void main(String[] args) throws IOException {
        String urlName;
        if (args.length > 0) urlName = args[0];
        else urlName = "http://horstmann.com";
        URL url = new URL(urlName);
        URLConnection connection = url.openConnection();
        if (args.length > 2) {
            String username = args[1];
            String password = args[2];
            String input = username + ":" + password;
            Base64.Encoder encoder = Base64.getEncoder();
            String encoding = encoder.encodeToString(input.getBytes(StandardCharsets.UTF_8));
            connection.setRequestProperty("Authorization", "Basic" + encoding);
        }
        connection.connect();
        Map> headers = connection.getHeaderFields();
        for (Map.Entry> entry : headers.entrySet()) {
            String key = entry.getKey();
            for (String value : entry.getValue())
                System.out.println(key + ":" + value);
        }
        System.out.println("----------------------");
        System.out.println("getContentType: " + connection.getContentType());
        System.out.println("getContentLength: " + connection.getContentLength());
        System.out.println("getContentEncoding: " + connection.getContentEncoding());
        System.out.println("getDate: " + connection.getDate());
        System.out.println("getExpiration: " + connection.getExpiration());
        System.out.println("getLastModify: " + connection.getLastModified());
        System.out.println("----------------------");
        String encoding = connection.getContentEncoding();
        if (encoding == null)
            encoding = "UTF-8";
        try (Scanner in = new Scanner(connection.getInputStream(), encoding)) {
            for (int n = 1; in.hasNextLine() && n <= 10; n++) {
                System.out.println(in.nextLine());
            }
            if (in.hasNextLine()) {
                System.out.println("...");
            }
        }
    }
}