如何在不关闭的情况下 'clean' InputStream？

Question

客户端代码片段。基本上它从标准输入读取并向服务器发送消息。

public static void main(String[] args) {

    try (Socket socket = new Socket("localhost", 1200)) {
        OutputStreamWriter writer = new OutputStreamWriter(socket.getOutputStream(), StandardCharsets.US_ASCII);

        Scanner scanner = new Scanner(System.in);
        for (String msg = scanner.nextLine(); !msg.equals("end"); msg = scanner.nextLine()) {
            writer.write(msg + "\n");
            writer.flush();
        }

    } catch (IOException e) {
        e.printStackTrace();
    }
}

服务器代码片段。打印来自流的消息。

 public void run() {

    try (InputStreamReader reader = new InputStreamReader(this.socket.getInputStream(), StandardCharsets
            .US_ASCII)) {

        StringBuilder builder = new StringBuilder();

        for (int c = reader.read(); c != -1; c = reader.read()) {

            builder.append((char) c);
            if ((char) c == '\n')
                System.out.print(builder);
        }

    } catch (IOException e) {
        e.printStackTrace();
    }
}

来自客户端的输入：

Text1
Text2

服务器输出：

Text1
Text1
Text2

我面临的问题是服务器不仅打印收到的消息，还打印之前的所有消息。

问题：如何在不关闭的情况下重置'clean' InputStream。如果这是不可能的，首选解决方案是什么？

Answer 1

您不需要 'clean' 流——您只需要在每一行之后重置缓冲区。使用 StringBuilder.setLength:

尝试如下操作

if (c == '\n') {
  System.out.print(builder.toString());
  builder.setLength(0);
}

另一方面，我强烈建议不要手动阅读这样的行。考虑使用 Scanner like you do in the client code or alternatively a BufferedReader.

try (final BufferedReader reader
         = new BufferedReader(new InputStreamReader(socket.getInputStream(), StandardCharsets.US_ASCII))) {
  for (String line = reader.readLine(); line != null; line = reader.readLine()) {
    System.out.println(line);
  }
} catch (final IOException ex) {
  ex.printStackTrace();
}

如何在不关闭的情况下 'clean' InputStream？

How to 'clean' InputStream without closing it?

java

sockets

inputstream