Java 我想要一个菜单在无效选项后重复？

Question

提问by user3769297

Ok I know this must be simpler than I am making it out to be, but I can't seem to figure it out. I have menu. the user selects a number which calls a certain method.

好吧，我知道这一定比我想象的要简单，但我似乎无法弄清楚。我有菜单。用户选择一个调用特定方法的号码。

I want the menu to repeat if they do not select a valid option. and then I want to give them the option to select another option or end the program.

如果他们没有选择有效选项，我希望菜单重复。然后我想给他们选择另一个选项或结束程序的选项。

Can anyone help me out?

谁能帮我吗？

import java.util.Scanner;


public class TestStringManip {
        //=================MAIN===============
    public static void main(String[] args) 
    {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter a string: ");
        String input = in.nextLine();

        StringManipulation newString = new StringManipulation(input);

        String menu = "\n Please select an option to perform"
                + "\n1 (1) Get all uppercase letters."
                + "\n2 (2) Get every second letter."
                + "\n3 (3) Replace vowels with _ "
                + "\n4 (4) Get a count of all vowels."
                + "\n5 (5) Get position of all vowels.";
        System.out.println(menu);
        int option = in.nextInt();


        do
        {
            if (option == 1)
            {
                newString.getUpperCase(input);
            }

            else if (option == 2)
            {
                newString.getEverySecond(input);
            }

            else
            {
                System.out.println("Error must select 1-5");
                System.out.println(menu);
                option = in.nextInt();
            }
        }while (option < 1 || option > 5);
    }

}

I have updated my code to try some of the suggested answers. It works for the first two options but that is it. I am also trying to get it to repeat after each option is chosen unless 0 is chosen which should end the program. Here is my updated code.

我已经更新了我的代码以尝试一些建议的答案。它适用于前两个选项，但仅此而已。我也试图让它在选择每个选项后重复，除非选择 0 应该结束程序。这是我更新的代码。

import java.util.Scanner;


public class TestStringManip {
        //=================MAIN===============
    public static void main(String[] args) 
    {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter a string: ");
        String input = in.nextLine();

        StringManipulation newString = new StringManipulation(input);

        String menu = "\n Please select an option to perform"
                + "\n1 (1) Get all uppercase letters."
                + "\n2 (2) Get every second letter."
                + "\n3 (3) Replace vowels with _ "
                + "\n4 (4) Get a count of all vowels."
                + "\n5 (5) Get position of all vowels."
                + "\n0 (0) Exit Program";
        System.out.println(menu);
        int option = in.nextInt();

        int i = 0;
        do
        {   
            if (option == 1)
            {
                newString.getUpperCase(input);
                i = 1;
            }

            else if (option == 2)
            {
                newString.getEverySecond(input);
                i = 1;
            }

            else if (option == 3)
            {
                newString.replaceVowels(input);
                i = 1;
            }

            else if (option == 4)
            {
                newString.getNumberOfVowels(input);
                i = 1;
            }

            else if (option == 5)
            {
                newString.getVowelPosition(input);
                i = 1;
            }

            else if (option == 0)
            {
                break;
            }

            else
            {
                System.out.println("Error must select 0-5");
                System.out.println("Enter your option: ");
                option = in.nextInt();
            }
        }while (i == 0);

    }

}

Answer 1

采纳答案by Frakcool

Not sure if this is what you want to do, repeat the whole menu unless user press 0, then exit.

不确定这是否是您想要做的，除非用户按0，否则重复整个菜单，然后退出。

I made it with switchinstead of if-else. But you can change that piece of code. Try it and tell me if this is what you were looking for.

我用switch而不是if-else. 但是您可以更改那段代码。试试吧，告诉我这是否是你要找的。

This one validates the input BEFORE processing it on switch

这个在开关上处理输入之前验证输入

import java.util.Scanner;

class MyTest {
    public static void main(String args[]) {
        int option;
        Scanner in = new Scanner(System.in);
        do {
            do {
                String menu = "\n Please select an option to perform"
                                + "\n1 (1) Get all uppercase letters."
                                + "\n2 (2) Get every second letter."
                                + "\n3 (3) Replace vowels with _ "
                                + "\n4 (4) Get a count of all vowels."
                                + "\n5 (5) Get position of all vowels."
                                + "\n0 (0) Exit Program";
                System.out.println(menu);
                option = in.nextInt();
            } while(option < 0 || option > 5); // This will make the menu repeat if option is higher than 6 or lowen than 0.

            switch(option) {
                case 1:
                    System.out.println("Option 1");
                    break;
                case 2:
                    System.out.println("Option 2");
                    break;
                case 3:
                    System.out.println("Option 3");
                    break;
                case 4:
                    System.out.println("Option 4");
                    break;
                case 5:
                    System.out.println("Option 5");
                    break;
                default:
                    System.out.println("Hasta la vista Baby");
                    break; //I always use this break, even when not needed.
            }
        } while (option != 0);
    }
}

EDIT

编辑

As GPRathourpointed out, you can do it with a simple do-whileloop, so it would look like this:

正如GPRathour指出的，你可以用一个简单的do-while循环来完成，所以它看起来像这样：

This one validates the input AFTER processing it on switch

这个在开关上处理输入后验证输入

import java.util.Scanner;

class MyTest {
    public static void main(String args[]) {
        int option;
        Scanner in = new Scanner(System.in);
        do {
            String menu = "\n Please select an option to perform"
            + "\n1 (1) Get all uppercase letters."
            + "\n2 (2) Get every second letter."
            + "\n3 (3) Replace vowels with _ "
            + "\n4 (4) Get a count of all vowels."
            + "\n5 (5) Get position of all vowels."
            + "\n0 (0) Exit Program";
            System.out.println(menu);
            option = in.nextInt();
            switch(option) {
                case 0:
                    System.out.println("Hasta la vista Baby");
                    break;
                case 1:
                    System.out.println("Option 1");
                    break;
                case 2:
                    System.out.println("Option 2");
                    break;
                case 3:
                    System.out.println("Option 3");
                    break;
                case 4:
                    System.out.println("Option 4");
                    break;
                case 5:
                    System.out.println("Option 5");
                    break;
                default:
                    System.out.println("Wrong option");
                    break; //I always use this break, even when not needed.
            }
        } while (option != 0);
    }
}

Answer 2

回答by Rook

Try a switch statement. Replace your if statement with this block of code.

尝试使用 switch 语句。用这段代码替换你的 if 语句。

do{
    switch(option){
        case 0:
             //Exit loop
             break;
        case 1:
             newString.getUpperCase(input);
             break;
        case 2:
             newString.getEverySecond(input);
             break;
        case 3:
             // Method number 3;
        . . .

        default:
            System.out.println("Please enter a number between 1 and 5");
            break;
    }
} while(option !=0)

EDITIf you want to know more about switch statements, check out this java tutorial

编辑如果您想了解有关 switch 语句的更多信息，请查看此java 教程

Re-edit:And yeah, you'll have to check for int input rather than a string like Ricky stated

重新编辑：是的，你必须检查 int 输入而不是像 Ricky 所说的字符串

Answer 3

回答by Kick Buttowski

code:

代码：

  public class TestStringManip {


public static void main(String[] args) {
    String menu = "\n Please select an option to perform"
            + "\n1 (1) for option one enter 1."
            + "\n2 (2) for option two enter 2."
            + "\n0 (0) Exit Program";
    Scanner in = new Scanner(System.in);
    int option = ReadAndMenu(menu,in);

    int i = 0;
    do {
        if (option == 1) {
            System.out.println("option one");
            option = ReadAndMenu(menu,in);
        } else if (option == 2) {
            System.out.println("option two");
            option = ReadAndMenu(menu,in);
        } else if (option == 0){
            System.out.println("exit");
            i= 1; 
        } else {
            System.out.println("Please enter a number between 1 and 2");
            option = ReadAndMenu(menu,in);

        }
    } while (i == 0);

}

 private static int ReadAndMenu(String menu, Scanner in){
        System.out.println(menu);
        System.out.print("Enter your option: ");
        return in.nextInt();
    }

}

output:

输出：

Please select an option to perform
1 (1) for option one enter 1.
2 (2) for option two enter 2.
0 (0) Exit Program
Enter your option: 1
option one

 Please select an option to perform
1 (1) for option one enter 1.
2 (2) for option two enter 2.
0 (0) Exit Program
Enter your option: 2
option two

 Please select an option to perform
1 (1) for option one enter 1.
2 (2) for option two enter 2.
0 (0) Exit Program
Enter your option: 5
Please enter a number between 1 and 2

 Please select an option to perform
1 (1) for option one enter 1.
2 (2) for option two enter 2.
0 (0) Exit Program
Enter your option: 0

Answer 4

回答by Ricky Mutschlechner

I would add a check to Scanner.hasNextInt() to make sure that the user is actually typing in an int. Because right now, if someone were to type "Hello", it would break your program. I fixed the code, and hopefully the loop.

我会向 Scanner.hasNextInt() 添加一个检查，以确保用户实际上输入的是 int。因为现在，如果有人输入“Hello”，它会破坏你的程序。我修复了代码，希望是循环。

Here's an example, using a modified version of your code: (sorry for the wonky indentation - yours is weird, and I haven't fixed it yet. Will edit with a fix)

这是一个示例，使用您的代码的修改版本：（抱歉缩进不稳定 - 您的缩进很奇怪，我还没有修复它。将编辑修复）

import java.util.Scanner;
public class TestStringManip {
    public static void main(String[] args) 
    {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter a string: ");
        String input = in.nextLine();

        StringManipulation newString = new StringManipulation(input);

        String menu = "\n Please select an option to perform"
                + "\n1 (1) Get all uppercase letters."
                + "\n2 (2) Get every second letter."
                + "\n3 (3) Replace vowels with _ "
                + "\n4 (4) Get a count of all vowels."
                + "\n5 (5) Get position of all vowels.";
        System.out.println(menu);

        int option = getIntInput(in);

        do{
            if (option == 1)
            {
                newString.getUpperCase(input);
            }

            else if (option == 2)
            {
                newString.getEverySecond(input);
            }

            else if (option == 0){
                System.out.println("Goodbye!");
                System.exit(0);
            }

            else
            {
                option = getIntInput(in);
            }

          }while(option != 0);
    }

  //this function will keep prompting until the user inputs a valid option
  int getIntInput(Scanner in){
     while(!in.hasNextInt()){
        System.out.println("Please enter a valid option (# between 1 and 5)");
     }

     return in.nextInt();
  }


}

Answer 5

回答by gprathour

The way you want your logic to work I believe there should be an option to exit too. So how about trying something like the following,

你希望你的逻辑工作的方式我相信也应该有一个退出的选项。那么尝试以下类似的方法如何，

do{
      String menu = "\n Please select an option to perform"
        + "\n1 (1) Get all uppercase letters."
        + "\n2 (2) Get every second letter."
        + "\n3 (3) Replace vowels with _ "
        + "\n4 (4) Get a count of all vowels."
        + "\n5 (5) Get position of all vowels."
        + "\n0 (0) To Exit.";
     System.out.println(menu);
     int option = in.nextInt();


    if (option == 1){
        newString.getUpperCase(input);
    }

    else if (option == 2){
        newString.getEverySecond(input);
    }
    ...
    ...
    else if(option == 0){
        break;
    }else{
        System.out.println("\n\nWrong Choice\n\n");
    }

}while(option != 0);

EDIT

编辑

As Kick Buttowski was having so many doubts. I created two simple examples, just run them on your own and see the output, as I don't have enough time to upload screenshots of output of both of them.

由于 Kick Buttowski 有很多疑问。我创建了两个简单的示例，只需自己运行它们并查看输出，因为我没有足够的时间上传它们的输出屏幕截图。

MyCodeit will work fine

MyCode它将正常工作

import java.util.Scanner;
class MyTest{
public static void main(String args[]){

    Scanner in = new Scanner(System.in);
 int option = 0;
    do{
  String menu = "\n Please select an option to perform"
    + "\n1 (1) Get all uppercase letters."
    + "\n2 (2) Get every second letter."
    + "\n3 (3) Replace vowels with _ "
    + "\n4 (4) Get a count of all vowels."
    + "\n5 (5) Get position of all vowels."
    + "\n0 (0) To Exit.";
 System.out.println(menu);

option = in.nextInt();



if (option == 1){
System.out.println("1");
}

else if (option == 2){
System.out.println("2");
}

else if(option == 0){
System.out.println("0");
    break;
}else{
    System.out.println("\n\nWrong Choice\n\n");
}

}while(option != 0);

}
}

To clarify the difference here is the Code proposed by Other userswhich will result into an infinite loop

澄清这里的区别是其他用户提出的代码，这将导致无限循环

import java.util.Scanner;
class MyTest2{
public static void main(String args[]){

    Scanner in = new Scanner(System.in);
 int option = 1;
    do{



if (option == 1){
System.out.println("1");
}

else if (option == 2){
System.out.println("2");
}

else if(option == 0){
System.out.println("0");
    break;
}else{
    System.out.println("\n\nWrong Choice\n\n");


  String menu = "\n Please select an option to perform"
    + "\n1 (1) Get all uppercase letters."
    + "\n2 (2) Get every second letter."
    + "\n3 (3) Replace vowels with _ "
    + "\n4 (4) Get a count of all vowels."
    + "\n5 (5) Get position of all vowels."
    + "\n0 (0) To Exit.";
 System.out.println(menu);

option = in.nextInt();



}

}while(option != 0);

}
}

Java 我想要一个菜单在无效选项后重复？

提问by user3769297

采纳答案by Frakcool

EDIT

编辑

回答by Rook

回答by Kick Buttowski

回答by Ricky Mutschlechner

回答by gprathour

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标签

Java 我想要一个菜单​​在无效选项后重复？

提问by user3769297

采纳答案by Frakcool

EDIT

编辑

回答by Rook

回答by Kick Buttowski

回答by Ricky Mutschlechner

回答by gprathour

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