How to format String variable that is entered by the user from this (00000000) to this (0000-0000)-CodePudding

I trying to figure out how to change the format of the variable that is entered by the user, all I found online is how to format already known values but nothing else really. the only thing is for sure is that the user is instructed to enter eight numbers only.

`System.out.print("Please enter your ID: ");
clientID = input.next();
System.out.println("Welcome "   clientName   "(Client ID: "   clientID   "), to yout invesment portfolio.");`

I tried to use the "String.format" method but I couldn't figure out how to edit the variable at a certain index.

CodePudding user response：

You can try this

clientID = String.format("%s-%s", clientID.substring(0, 4), clientID.substring(4));

Or this

clientID = clientID.substring(0, 4)   "-"   clientID.substring(4);

CodePudding user response：

You can also use some regex for this kind of tasks. In this simple case, it is probably a little bit overkill, but in general with regex, you are a lot more flexible.

public class MyClass {
    public static void main(String args[]) {
      String pattern = "^(\\d{4})(\\d{4})$";
      
      String input = "12345678";
      String parsedInput = input.replaceAll(pattern, "$1-$2");

      System.out.println(parsedInput);
    }
}

First you define your pattern. In this case we say that we have two blocks ^(...)(...)$ where each contains exactly 4 {4} numbers \d. With the replaceAll function, you then can rearrange these earlier defined blocks. They simply get numberd in order of appearance in the pattern. So $1 references the first block, $2 the second, and so on. With that you can simply add the hypen in between the two blocks with $1-$2