代码:
import java.io.*;
import java.net.*;public class ServerSocket {
    public static void main(String[] args) throws IOException {        ServerSocket serverSocket = null;
        try {
            serverSocket = new ServerSocket(1234);
        } catch (IOException e) {
            System.err.println("Could not listen on port: 1234.");
            System.exit(1);
        }        Socket clientSocket = null;
        try {
            clientSocket = serverSocket.accept();
        } catch (IOException e) {
            System.err.println("Accept failed.");
            System.exit(1);
        }        PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
        BufferedReader in = new BufferedReader(
new InputStreamReader(
clientSocket.getInputStream()));
        String inputLine, outputLine;        while ((inputLine = in.readLine()) != null) {
            outputLine=inputLine;
             out.println(outputLine);
             if (outputLine.equals("Bye"))
                break;
        }
        out.close();
        in.close();
        clientSocket.close();
        serverSocket.close();
    }
}
每次编译时都会报错:
ServerSocket.java:9: 找不到符号
符号: 构造函数 ServerSocket(int)
位置: 类 ServerSocket
            serverSocket = new ServerSocket(1234);
                           ^
ServerSocket.java:17: 找不到符号
符号: 方法 accept()
位置: 类 ServerSocket
            clientSocket = serverSocket.accept();
                                       ^
ServerSocket.java:43: 找不到符号
符号: 方法 close()
位置: 类 ServerSocket
        serverSocket.close();我已经把包含ServerSocket的Java.net.*包含进去了.为什么还报错呢?