サンプル

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;

public class Main {

  public static void main(String[] args) {
    try {
      System.out.println("-= Get -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");
      System.out.println(getContent("http://www.alc.co.jp/", false));
      System.out.println("-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");

      System.out.println("-= Post -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");
      System.out.println(getContent("http://www.msn.com/ja-jp", true));
      System.out.println("-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=");
    } catch (IOException ex) {
      ex.printStackTrace();
    }

  }

  /**
   * コンテンツ取得
   * @param targetUrl URL
   * @param isPost POST通信か
   * @return コンテンツ
   * @throws IOException
   */
  private static String getContent(String targetUrl, boolean isPost) throws IOException {
    URL url = new URL(targetUrl);

    HttpURLConnection connection = null;
    try {
      connection = (HttpURLConnection) url.openConnection();
      connection.setRequestProperty("Accept-Language", "ja");
      
      if (isPost) {
        connection.setDoOutput(true);
        connection.setRequestMethod("POST");

        BufferedWriter writer = new BufferedWriter(
            new OutputStreamWriter(connection.getOutputStream(), StandardCharsets.UTF_8));
        writer.write(System.getProperty("line.separator"));
        writer.flush();
      } else {
        connection.setRequestMethod("GET");
      }

      if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
        System.out.println("Error : " + connection.getResponseCode());
        return null;
      }

      try (
          InputStreamReader inputStreamReader = new InputStreamReader(connection.getInputStream(),
              StandardCharsets.UTF_8);
          BufferedReader bufferedReader = new BufferedReader(inputStreamReader)) {
        StringBuilder returnValue = new StringBuilder();
        String line;
        while ((line = bufferedReader.readLine()) != null) {
          returnValue.append(line);
          //returnValue.append(System.getProperty("line.separator"));
        }
        return returnValue.toString();
      }
    } finally {
      if (connection != null) {
        connection.disconnect();
      }
    }
  }
}

出力結果

-= Get -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w ・・・略・・・
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
-= Post -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE HTML PUBLIC "-//WAPFORU ・・・略・・・
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=