java - 为什么在http请求中编码？

Question

我正在尝试在 Java 上使用 http 协议(protocol)从服务器学习请求和检索数据这是我在 Oracle>教程>网络上找到的代码(代码粘贴在问题的底部)

问题 1: out.write("string="+ stringToReverse);为什么 "string="没有被编码？像 stringToReverse 变量

String stringToReverse = URLEncoder.encode(args[1], "UTF-8");

问题 2:下面有两段代码，一段来自 oracle 代码，另一段来自 android studio tuts

oracle tuts 中的代码

BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));

---

android tuts 代码

inputStream = urlConnection.getInputStream();    
InputStreamReader inputStreamReader = new InputStreamReader(inputStream, Charset.forName("UTF-8"));
                BufferedReader reader = new BufferedReader(inputStreamReader);

为什么 Oracle 代码中缺少 Charset.forName("UTF-8")？

---

注意:从基础开始解释非常有用:)

import java.io.*;
import java.net.*;

public class Reverse {
public static void main(String[] args) throws Exception {

    if (args.length != 2) {
        System.err.println("Usage:  java Reverse "
            + "http://<location of your servlet/script>"
            + " string_to_reverse");
        System.exit(1);
    }

    String stringToReverse = URLEncoder.encode(args[1], "UTF-8");

    URL url = new URL(args[0]);
    URLConnection connection = url.openConnection();
    connection.setDoOutput(true);

    OutputStreamWriter out = new OutputStreamWriter(
                                     connection.getOutputStream());
    out.write("string=" + stringToReverse);
    out.close();

    BufferedReader in = new BufferedReader(
                                new InputStreamReader(
                                connection.getInputStream()));
    String decodedString;
    while ((decodedString = in.readLine()) != null) {
        System.out.println(decodedString);
    }
    in.close();
}
}

Answer 1

问题 1:

无需对“string=”进行编码(因为它不包含任何特殊字符，如 https://docs.oracle.com/javase/6/docs/api/java/net/URLEncoder.html 中所述)

问题 2:

以下示例中的字符集未明确定义:

BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));

因此使用默认字符集(可能不是 UTF-8)

Every instance of the Java virtual machine has a default charset, which may or may not be one of the standard charsets. The default charset is determined during virtual-machine startup and typically depends upon the locale and charset being used by the underlying operating system. (https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html)