while循环，错误处理，尝试，捕获

Question

由于错误异常处理，我提前退出循环，因为我使用以下行编辑了代码：

try {
    cmd = Command.valueOf(command.toUpperCase());
} catch (IllegalArgumentException e) {
    System.out.println("Invalid input");
    return;
}

只想退出EXIT案例

CODE：

package ui;

import java.util.Scanner;

public class Application {

    static String command;

    public enum Command {

        CONNECT, DISCONNECT, SEND, LOGLEVEL, HELP, QUIT, EXIT
    }

    private static void run(Scanner sc) {

        System.out.println("Milestone1: Connection and interation with TCP server");
        // String command; // ready for the input

        boolean done = false; // ready for the menu loop
        while (!done) { // keep on until done

            System.out.println("\n-------------------Please select one of the commands-------------------------------------");
            System.out.println("\nCONNECT, DISCONNECT, SEND, LOGLEVEL, HELP, QUIT, EXIT");

            command = sc.nextLine(); // take user input         
            Command cmd = null;

            try {
                cmd = Command.valueOf(command.toUpperCase());
            } catch (IllegalArgumentException e) {
                System.out.println("Invalid input");
               return;
            }
            switch (cmd) {

                case EXIT: // exit menu
                    done = true;// condition for breaking the loop
                    break;

                case CONNECT:

                    System.out.println(" IP adress: ");
                    String userInput = sc.next(); // user Input

                    try {
                        System.out.println(" Port: ");

                        int userInput1 = sc.nextInt();// user Input

                        if (userInput1 >= 0) {

                            System.out.println(" EcoClient>" + " " + command + " " + userInput + " "
                                    + userInput1);
                        } else {
                            System.out
                                    .println("Entered value for Port is negative number or IP adress length < 7 || > 15, not in n.n.n.n format ");
                        }

                    } catch (Exception e) {// throw exception in case of illogical
                        // input
                        System.out.println("\nBad input, please try again ");
                        sc.nextLine(); // remove leftover "\n"
                    }

                    break;

                case DISCONNECT:

                    System.out.println(" EcoClient>" + " " + command);

                    break;

                case SEND:

                    System.out
                            .println("Please enter " + " Hello World ");
                    try {
                        String userInput2 = sc.next(); // user Input
                        System.out.println(" EcoClient>" + " " + command + " "
                                + userInput2);

                    } catch (Exception e) {// throw exception in case of illogical
                        // input

                        System.out.println("\nBad input, please try again ");
                        sc.nextLine(); // remove leftover "\n"
                    }
                    break;

                case LOGLEVEL:
                    try {
                        System.out.println(" EcoClient>" + " " + command + "< "
                                + "current log status" + " >");
                    } catch (Exception e) {// throw exception in case of illogical
                        // input

                        System.out.println("\nBad input, please try again ");
                        sc.nextLine(); // remove leftover "\n"

                    }
                    break;

                case HELP:
                    try {
                        System.out
                                .println("Following set of commands provide following functionalities:"
                                        + " connect: establishes connection to the eco server "
                                        + "disconnect: disconnects from the server and receives confirmation message "
                                        + "send: sends the message to the server "
                                        + "logLevel: prints out current log status"
                                        + "quit: quits and notifies user about program shut down "
                                        + "exit: cancel the input");

                    } catch (Exception e) {// throw exception in case of illogical
                        // input

                        System.out.println("\nBad input, please try again ");
                        sc.nextLine(); // remove leftover "\n"
                    }
                    break;

                case QUIT:

                    try {
                        System.out.println(" EcoClient> " + command);

                    } catch (Exception e) {// throw exception in case of illogical
                        // input

                        System.out.println("\nBad input, please try again ");
                        sc.nextLine(); // remove leftover "\n"

                    }
                    break;

                default:
                    System.out.println("Does not recognise "
                            + "the input, pl. try again");

            }

        }
    }

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);// will take user input

        run(sc);

    }
}

Answer 1

看起来您想使用continue（开始下一个循环迭代）而不是return。

Answer 2

public enum Command {
    CONNECT, DISCONNECT, SEND, LOGLEVEL, HELP, QUIT, EXIT, XX
}

try {
    cmd = Command.valueOf(command.toUpperCase());
} catch (IllegalArgumentException e) {
    System.out.println("Invalid input");
    cmd = XX;
}