套接字编程，麻烦与尝试循环

Question

我一直在看Oracle教程网站学习基本的套接字编程。我试图在eclipse上上传示例，但当我试图编译时，括号所在的语法有错误。为什么会发生这种情况?谢谢。

try (
        Socket echoSocket = new Socket(hostName, portNumber);
        PrintWriter out =
            new PrintWriter(echoSocket.getOutputStream(), true);
        BufferedReader in =
            new BufferedReader(
                new InputStreamReader(echoSocket.getInputStream()));
        BufferedReader stdIn =
            new BufferedReader(
                new InputStreamReader(System.in))
    ) {
        String userInput;
        while ((userInput = stdIn.readLine()) != null) {
            out.println(userInput);
            System.out.println("echo: " + in.readLine());
        }
    } catch (UnknownHostException e) {
        System.err.println("Don't know about host " + hostName);
        System.exit(1);
    } catch (IOException e) {
        System.err.println("Couldn't get I/O for the connection to " +
            hostName);
        System.exit(1);
    } 

Answer 1

为什么会发生这种情况?

您正在尝试"尝试使用资源"。这需要Java 7或更高版本。请确保您的eclipse项目也设置为Java 7，而不仅仅是本地命令行JDK。

http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html