java - 为什么新的 InputStreamReader 不会读取控制台中的剩余字符？

Question

所以我有一个用 Java 编写的非常简单的服务器:

public class SimpleServer {
    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = new ServerSocket(8888);
        System.out.println("Server Socket created, waiting for client...");
        Socket accept = serverSocket.accept();
        InputStreamReader inputStreamReader = new InputStreamReader(accept.getInputStream());
        int read;
        System.out.println("Client connected, waiting for input");
        while ((read = inputStreamReader.read()) != -1) {
            System.out.print((char) read);
        }
    }
}

这是我用来连接它的代码:

public class SimpleClient {

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

        Socket socket = new Socket("localhost",8888);
        OutputStreamWriter outputStream = new OutputStreamWriter(socket.getOutputStream());

        InputStreamReader inputStreamReader;
        char[] chars = new char[5];

        while (true) {
            System.out.println("Say something: ");
            inputStreamReader = new InputStreamReader(System.in);
            inputStreamReader.read(chars);
            int x = 0;
            for (int i=0;i<5;i++) {
                if(chars[i]!='\u0000') {
                    x++;
                }
            }
            outputStream.write(chars,0,x);
            outputStream.flush();
            chars = new char[5];
        }

    }

}

现在，当我在客户端的终端中输入这样的内容时:

123456789

我将在服务器的终端中看到:

Server Socket created, waiting for client...
Client connected, waiting for input
12345

但是，当我按如下方式更改客户端时:

public class SimpleClient {

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

        Socket socket = new Socket("localhost",8888);
        OutputStreamWriter outputStream = new OutputStreamWriter(socket.getOutputStream());

        InputStreamReader inputStreamReader = new InputStreamReader(System.in);
        char[] chars = new char[5];

        while (true) {
            System.out.println("Say something: ");
            inputStreamReader.read(chars);
            int x = 0;
            for (int i=0;i<5;i++) {
                if(chars[i]!='\u0000') {
                    x++;
                }
            }
            outputStream.write(chars,0,x);
            outputStream.flush();
            chars = new char[5];
        }

    }

}

然后对于相同的输入，我会看到:

Server Socket created, waiting for client...
Client connected, waiting for input
123456789

我的问题是，System.out 是一个静态变量，在本例中它已经打开并连接到终端。为什么创建新的InputStreamReader对象时终端中的信息会丢失？相同的终端被传递给对象，不是吗？

Answer 1

Why is the information in the terminal lost when a new InputStreamReader object is created?

当您在 InputStreamReader 上调用 read() 时，它允许(并且通常会)从流中读取比您实际请求的更多的数据，并存储其余的在缓冲区中，以满足稍后的读取调用。我怀疑整个文本行实际上已被第一个 InputStreamReader 读取，因此当您为同一流构造第二个 InputStreamReader 时，没有任何内容可供它读取，您必须输入更多文本才能让它执行任何操作。