如何在没有用户输入的情况下自动返回主菜单?

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标题翻译

How to automatically return to main menu without user input?

问题

class myOwnTryAginLoopThatWorks {
    public static void main(String[] args) {
        Scanner console = new Scanner(System.in);
        boolean valid;
        char choice = '\0';
        String persnr;
        do {
            valid = true;
            System.out.print("请输入字母 P T L S A 或 Q:"); // 菜单
            String input = console.nextLine();
            if (!isValid(input)) {
                valid = false;
                System.out.print("您未输入正确的菜单选项,");
                if (input.length() != 1) {
                    System.out.println("并且您的输入过长(必须为 1 个字符),");
                    valid = false;
                }
            }
            choice = input.charAt(0);
        } while (!valid);

        switch (choice) {
            case 'P':
                do {
                    valid = true;
                    System.out.print("以 (YYYYMMDD) 格式输入 persnr:");
                    try {
                        persnr = console.nextLine();
                        if (!persnr.matches("[1-9]{1}[0-9]{7}")) {
                            throw new IllegalArgumentException("您输入的格式有误,请重试");
                        }
                        System.out.println("处理中...");
                    } catch (IllegalArgumentException e) {
                        System.out.println(e.getMessage());
                        valid = false;
                    }
                } while (!valid);
                break;
        }

        System.out.print("请输入名字:");
        String firstName = console.nextLine();
        System.out.print("请输入姓氏:");
        String surName = console.nextLine();

    }

    public static boolean isValid(String n) {
        switch (n) {
            case "P":
            case "T":
            case "L":
            case "S":
            case "A":
            case "Q":
                return true;
            default:
                return false;
        }
    }
}
英文翻译

The "main menu" is the place where System.out.print("enter letter P T L S A or Q");. When the user has entered his/her surname, the console should automatically return to the first System.out.print statement i.e the menu. How do I set it up to be like that?

class myOwnTryAginLoopThatWorks{
	public static void main (String [] args){
		Scanner console = new Scanner(System.in);
		boolean valid;
		char choice = '\0';
		String persnr;
		do{
			valid = true;
			System.out.print("enter letter P T L S A or Q"); //menu
			String input = console.nextLine();
			if (!isValid(input)){
				valid = false;
				System.out.print("You did not enter the correct menu option, ");
				if (input.length() != 1) {
					System.out.println("and your input length is too long (must be 1 character long), ");
					valid = false;
				}
			}
			choice = input.charAt(0);
		}while(!valid);
		
		switch (choice) {
			case 'P':
					do {
						valid = true; 
						System.out.print("Enter persnr in the format of (YYYYMMDD): ");
						try {
							persnr = console.nextLine();
							if (!persnr.matches("[1-9]{1}[0-9]{7}")) {
								throw new IllegalArgumentException("You printed wrong format, try again");
							}
							System.out.println("Processsing...");
						} catch (IllegalArgumentException e) {
						System.out.println(e.getMessage());
						valid = false;
						}
					} while (!valid);
					break;
		}

		System.out.print("enter first name ");
		String firstName = console.nextLine();
		System.out.print("enter surrname ");
		String surName = console.nextLine();
		
	} 

	public static boolean isValid (String n){ 
		switch(n){
			case "P":
			case "T":
			case "L":
			case "S":
			case "A":
			case "Q":
					return true;
			default:
					return false;
		}
	}    
}

答案1

得分: 2

private static boolean exit = false;
public static void main(String[] args) {
    
    while (exit == false){
         readValues();
    }
}

private static boolean isValid(String n) {

    switch (n) {
    case "P":
    case "T":
    case "L":
    case "S":
    case "A":
    case "Q":
        return true;
    default:
        return false;

    }
}

private static void readValues() {
    Scanner console = new Scanner(System.in);

    boolean valid;
    char choice = '\0';
    String persnr;

    do {
        valid = true;
        System.out.print("enter letter P T L S A or Q"); //menu
        String input = console.nextLine();

        if (!isValid(input)) {
            valid = false;
            System.out.print("You did not enter the correct menu option, ");

            if (input.length() != 1) {
                System.out.println("and your input length is too long (must be 1 character long), ");
                valid = false;
            }
        }

        choice = input.charAt(0);

    } while (!valid);

    switch (choice) {
    case 'P':

        do {
            valid = true;
            System.out.print("Enter DATE in the format of (YYYYMMDD): ");

            try {
                persnr = console.nextLine();

                if (!persnr.matches("[1-9]{1}[0-9]{7}")) {
                    throw new IllegalArgumentException("You printed wrong format, try again");
                }

                System.out.println("Processsing...");

            } catch (IllegalArgumentException e) {
                System.out.println(e.getMessage());
                valid = false;
            }

        } while (!valid);
        break;

    }

    System.out.print("enter first name ");
    String firstName = console.nextLine();

    System.out.print("enter surrname ");
    String surName = console.nextLine();

    String query = " insert into Person (PNr, FName, ENamn)"
         + " values (persnr, firstName, surName)";

}
英文翻译

> You MUST ask the question better. As I understand it, you need your menu is shown again asking to enter another data.

private static boolean exit = false;
public static void main(String[] args) {
	
	while (exit == false){
		 readValues();
	}
	

}

private static boolean isValid(String n) {

	switch (n) {
	case "P":
	case "T":
	case "L":
	case "S":
	case "A":
	case "Q":
		return true;
	default:
		return false;

	}
}

private static void readValues() {
	Scanner console = new Scanner(System.in);

	boolean valid;
	char choice = '\0';
	String persnr;

	do {
		valid = true;
		System.out.print("enter letter P T L S A or Q"); //menu
		String input = console.nextLine();

		if (!isValid(input)) {
			valid = false;
			System.out.print("You did not enter the correct menu option, ");

			if (input.length() != 1) {
				System.out.println("and your input length is too long (must be 1 character long), ");
				valid = false;
			}
		}

		choice = input.charAt(0);

	} while (!valid);

	switch (choice) {
	case 'P':

		do {
			valid = true;
			System.out.print("Enter DATE in the format of (YYYYMMDD): ");

			try {
				persnr = console.nextLine();

				if (!persnr.matches("[1-9]{1}[0-9]{7}")) {
					throw new IllegalArgumentException("You printed wrong format, try again");
				}

				System.out.println("Processsing...");

			} catch (IllegalArgumentException e) {
				System.out.println(e.getMessage());
				valid = false;
			}

		} while (!valid);
		break;

	}

	System.out.print("enter first name ");
	String firstName = console.nextLine();

	System.out.print("enter surrname ");
	String surName = console.nextLine();

	String query = " insert into Person (PNr, FName, ENamn)"
		 + " values (persnr, firstName, surName)";

}

huangapple
  • 本文由 发表于 2020年3月16日 23:22:36
  • 转载请务必保留本文链接:https://java.coder-hub.com/60708672.html
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