在用户输入的Ctrl + Z上终止Java程序

Question

I have following code:

        String inputString;
        Scanner in = new Scanner(System.in);
        while (true) {
            System.out.print("jcp>");
            inputString = in.nextLine();

            String[] tokens = inputString.split(" ");
            switch (tokens[0]) {
                case "new":
                    createNewInstance(tokens);
                    break;
                case "call":
                    callMethod(tokens);
                    break;
                case "print":
                    Object obj = hashMap.get(tokens[1]);
                    print(obj);
                    break;
                default:
                    System.out.println("Illegal command!");
                    break;
            }
        }

I simply want the program to break out of while loop when user hits ctrl+Z

Answer 1

nextLine() will throw NoSuchElementException when the stream has reached its end. Or you can use in.hasNextLine().

Answer 2

Ctrl+Z to exit the program would be bad, Ctrl+C|Ctrl+D already ends the program execution on terminal, so it would be good the same way you expect users to type in commands, tell them to type exit as the command to EXIT your program and shortcuts like x or e can be used instead of complete word.

How about following code,

String inputString;
Scanner in = new Scanner(System.in);
while (true) {
    System.out.print("jcp>");
    inputString = in.nextLine();
    String[] tokens = inputString.split(" ");
    switch (tokens[0]) {
        case "n":
        case "new":
            createNewInstance(tokens);
            break;
        case "c":
        case "call":
            callMethod(tokens);
            break;
        case "p":
        case "print":
            Object obj = hashMap.get(tokens[1]);
            print(obj);
            break;
        case "e":
        case "x":
        case "exit":
            return;
        default:
            System.out.println("Illegal command!");
            break;
    }
}

If return; won't work you can replace that with System.exit(0);