java - 在 switch 语句中使用 switch 语句是否可以接受？

Question

我知道我的文档并不出色。

该程序用于创建石头剪刀布游戏:

我最初很难让案例陈述与案例陈述一起正常工作，但我觉得我解决了这个问题。

我的问题:这是在 switch 语句中嵌套 switch 语句的可接受的实现吗？否则，我可以在 userChoice Switch 语句中放入 if 语句。

public static void main(String[] args) {

    // Variable declarations
    Scanner keyboard = new Scanner(System.in);
    Random rand = new Random();
    int sentinel = 4;
    int userChoice;
    int computerChoice;

    // Display Rock, Paper, Scissors menu
    menu();

    // Obtain user's choice
    userChoice = validOption("\nPlease make a selection: ", 1, 4);

    // Display game results
    while (userChoice != sentinel) {
        switch (userChoice) {
            case 1:
                // Generate computer's choice
                computerChoice = rand.nextInt(3) + 1; 
                System.out.println("Computer's choice: " + computerChoice);

                // Determine outcome of the round
                switch (computerChoice) {
                    case 1:
                        System.out.println("Rock cannot defeat Rock. Draw.");
                        break;
                    case 2:
                        System.out.println("Paper covers Rock. Computer wins.");
                        break;
                    case 3:
                        System.out.println("Rock smashes Scissors. You win!");
                        break;
                }
                // Display menu selection and obtain user choice
                menu();
                userChoice = validOption("\nPlease make a selection: ", 1, 4);
                break;

            case 2: 
                // Generate computer's choice
                computerChoice = rand.nextInt(3) + 1; 
                System.out.println("Computer's choice: " + computerChoice);

                // Determine outcome of the round
                switch (computerChoice) {
                    case 1:
                        System.out.println("Paper covers Rock. You win!");
                        break;
                    case 2:
                        System.out.println("Paper cannot defeat Paper. Draw.");
                        break;     
                    case 3:
                        System.out.println("Scissors cut Paper. Computer wins.");
                        break;
                }
                //Display menu selection and obtain user choice
                menu();
                userChoice = validOption("\nPlease make a selection: ", 1, 4);
                break;

            case 3:
                // Generate computer's choice
                computerChoice = rand.nextInt(3) + 1; 
                System.out.println("Computer's choice: " + computerChoice);
                // Determine outcome of the round
                switch (computerChoice) {
                    case 1:
                        System.out.println("Rock smashes Scissors. Computer wins.");
                        break;
                    case 2:
                        System.out.println("Scissors cut Paper. You win!");
                        break;
                    case 3:
                        System.out.println("Scissors cannot defeat Scissors. Draw.");
                        break;
                }
                // Display menu selection and obtain user choice
                menu();
                userChoice = validOption("\nPlease make a selection: ", 1, 4);
                break;
        }
    }     
    System.out.println("Game Over.");
}

// Create menu method
public static void menu () {
    System.out.println("\n1 = Rock");
    System.out.println("2 = Paper");
    System.out.println("3 = Scissors");
    System.out.println("4 = End Game\n");
}

/**
 * Protects option input from incorrect value (non-numeric, too high or too low)
 * @param prompt
 * @param minValue
 * @param maxValue
 * @return 
 */
public static int validOption (String prompt,
                                int minValue,
                                int maxValue) {
    Scanner keyboard = new Scanner (System.in);
    int value;
    String errorMessage = "Incorrect value. Please select options "
            + "1, 2, 3 or 4\n";
    do {
        System.out.print(prompt);
        if (keyboard.hasNextInt()) {
            value = keyboard.nextInt();
            if (value < minValue || value > maxValue) {
                System.out.println(errorMessage);
            } else {
                break; // Exit loop.
            }
        } else {
            System.out.println(errorMessage);
        }
        keyboard.nextLine(); // Clears buffer.
    } while (true);
    return value;
}

}

Answer 1

恕我直言，只要可读，在 switch 语句内编写 switch 语句本身就可以。为了使代码更具可读性，您可以使用常量而不是 1、2、3 来引用选项:

final int ROCK = 1;
final int PAPER = 1;
final it SCISSORS  = 1;

您的开关可能如下所示:

switch (computerChoice) {
    case ROCK:
        System.out.println("Rock cannot defeat Rock. Draw.");
        break;
    case PAPER:
        System.out.println("Paper covers Rock. Computer wins.");
        break;
    case SCISSORS:
        System.out.println("Rock smashes Scissors. You win!");
        break;
}

您可以改进的另一件事是将这两个部分移出外部开关:

// Generate computer's choice
computerChoice = rand.nextInt(3) + 1; 
System.out.println("Computer's choice: " + computerChoice);

// and

menu();
userChoice = validOption("\nPlease make a selection: ", 1, 4);

因为您在每种情况下都这样做。

您还可以将内部 switch 语句提取到如下方法中:

private static handlePlayerRock() {
    // add the inner switch for the case ROCK of the outer switch here
}

private static handlePlayerScissors() {
    // add the inner switch for the case SCISSORS of the outer switch here
}

private static handlePlayerPaper() {
    // add the inner switch for the case PAPER of the outer switch here
}

您的开关将如下所示:

switch (userChoice) {
    case ROCK: handlePlayerRock();
    case PAPER: handlePlayerPaper();
    case SCISSORS: handlePlayerScissors();
}

除了嵌套开关之外，还有更高级的方法可以解决此问题。你可以把所有的可能性都放进一个 HashMap<Combination, String> ，其中Combination是代表玩家和计算机选择的类。该 map 将包含以下内容:

(ROCK, ROCK) -> "Rock cannot defeat Rock. Draw."
(ROCK, PAPER) -> "Paper covers Rock. Computer wins."
...

您可以使用计算机和玩家的选择来访问与 key 关联的值。