Question

How to add spaces to a number every 4 digits in Java

Answer 1

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Program {
    public static String formatCardNumber(String cardNumber) {
        Pattern pattern = Pattern.compile(".{4}");
        Matcher matcher = pattern.matcher(cardNumber);
        
        StringBuilder sb = new StringBuilder();
        while (matcher.find()) {
            sb.append(matcher.group()).append(" ");
        }
        
        return sb.toString().trim();
    }
    
    public static void main(String[] args) {
        String cardNumber = "9003125334656789";
        
        String cardNumberWithSpaces = formatCardNumber(cardNumber);
        
        System.out.println(cardNumberWithSpaces);
    }
}


 
/*
run
 
9003 1253 3465 6789
 
*/

 

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Answer 2

public class Program {
    public static void main(String[] args) {
        String cardNumber = "9003125334656789";

        String cardNumberWithSpaces = cardNumber.replaceAll(".{4}", "$0 ");

        System.out.println(cardNumberWithSpaces);
    }
}


 
/*
run
 
9003 1253 3465 6789
 
*/

 

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