I need to prase integers after a specific character from list of strings

Question

i got a problem here guys. I need to get all the numbers from a string here from a list of strings.

Lets say one of the strings in the list is "Jhon [B] - 14, 15, 16" and the format of the strings is constant, every string has maximum of 7 numbers in it and the numbers are separated with "," . I want to get every number after the "-". i am really confused here, i tried everything i know of but i am not getting even close.

public static List<String> readInput() {
    final Scanner scan = new Scanner(System.in);
    final List<String> items = new ArrayList<>();
    while (scan.hasNextLine()) {
        items.add(scan.nextLine());
    }
    return items;
}

public static void main(String[] args) {
    final List<String> stats= readInput();
    
}

}

Answer 1

You could...

Just manually parse the String using things like String#indexOf and String#split (and String#trim)

String text = "Jhon [B] - 14, 15, 16";
int indexOfDash = text.indexOf("-");
if (indexOfDash < 0 && indexOfDash + 1 < text.length()) {
    return;
}
String trailingText = text.substring(indexOfDash + 1).trim();
String[] parts = trailingText.split(",");
// There's probably a really sweet and awesome
// way to use Streams, but the point is to try
// and keep it simple ?
List<Integer> values = new ArrayList<>(parts.length);
for (int index = 0; index < parts.length; index++) {
    values.add(Integer.parseInt(parts[index].trim()));
}

System.out.println(values);

which prints

[14, 15, 16]

You could...

Make use of a custom delimiter for Scanner for example...

String text = "Jhon [B] - 14, 15, 16";

Scanner parser = new Scanner(text);
parser.useDelimiter(" - ");
if (!parser.hasNext()) {
    // This is an error
    return;
}
// We know that the string has leading text before the "-"
parser.next();
if (!parser.hasNext()) {
    // This is an error
    return;
}
String trailingText = parser.next();

parser = new Scanner(trailingText);
parser.useDelimiter(", ");
List<Integer> values = new ArrayList<>(8);
while (parser.hasNextInt()) {
    values.add(parser.nextInt());
}

System.out.println(values);

which prints...

[14, 15, 16]

Answer 2

You can use simple String operations like:

public static List<String> readInput() {
    
    String text = "Jhon [B] - 14, 15, 16";
    String numbersOnly = text.substring(text.indexOf("-") + 1).trim();
    return Arrays.stream(numbersOnly.split(",")).collect(Collectors.toList());
}

public static void main(String[] args) {
    final List<String> stats = readInput();

}

Answer 3

Or You could use a method that will extract signed or unsigned Whole or floating point numbers from a string. The method below makes use of the String#replaceAll() method:

/**
 * This method will extract all signed or unsigned Whole or floating point 
 * numbers from a supplied String. The numbers extracted are placed into a 
 * String[] array in the order of occurrence and returned.<br><br>
 * 
 * It doesn't matter if the numbers within the supplied String have leading 
 * or trailing non-numerical (alpha) characters attached to them.<br><br>
 * 
 * A Locale can also be optionally supplied so to use whatever decimal symbol 
 * that is desired otherwise, the decimal symbol for the system's current 
 * default locale is used. 
 * 
 * @param inputString (String) The supplied string to extract all the numbers 
 * from.<br>
 * 
 * @param desiredLocale (Optional - Locale varArgs) If a locale is desired for a 
 *               specific decimal symbol then that locale can be optionally 
 *               supplied here. Only one Locale argument is expected and used 
 *               if supplied.<br>
 * 
 * @return (String[] Array) A String[] array is returned with each element of 
 *               that array containing a number extracted from the supplied 
 *               Input String in the order of occurrence.
 */
public static String[] getNumbersFromString(String inputString, java.util.Locale... desiredLocale) {
    // Get the decimal symbol the the current system's locale.
    char decimalSeparator = new java.text.DecimalFormatSymbols().getDecimalSeparator();
    
    /* Is there a supplied Locale? If so, set the decimal 
       separator to that for the supplied locale       */
    if (desiredLocale != null && desiredLocale.length > 0) {
        decimalSeparator = new java.text.DecimalFormatSymbols(desiredLocale[0]).getDecimalSeparator();
    } 
    /* The first replaceAll() removes all dashes (-) that are preceeded
       or followed by whitespaces. The second replaceAll() removes all
       periods from the input string except those that part of a floating 
       point number. The third replaceAll() removes everything else except 
       the actual numbers. */
   return  inputString.replaceAll("\\s*\\-\\s{1,}","")
                      .replaceAll("\\.(?![\\d](\\.[\\d])?)", "")
                      .replaceAll("[^-?\\d+" + decimalSeparator + "\\d+]", " ")
                      .trim().split("\\s+");
}