javastringsplitstringbuilder

How to splite with number with , in filed with missing number in given number?

I am trying to getting this output. But failed to missing numbers in separate by this ',' one ?

Input: 1, 2, 3, 4.. 9, 10,13.. 17, 18, 19.. 25 
Output: 1 2 3 4 5 6 7 8 9 10 13 14 15 16 17 18 19 20 21 22 23 24 25
Solution

  • Here is a working implementation which does what you need, further explanation below the code:

    public static String getCSV(int start, int end) {
    List<String> list = IntStream.range(start, end).boxed()
       .map(i -> i.toString()).collect(Collectors.toList());
    String csv = String.join(" ", list);

    return csv;
}

public static void main(String args[])
{
    String input = "1, 2, 3, 4.. 9, 10,13.. 17, 18, 19.. 25";
    input = input.replaceAll(",\\s*", " ");
    Pattern r = Pattern.compile("(\\d+)\\.\\.\\s*(\\d+)");
    Matcher m = r.matcher(input);
    StringBuffer stringBuffer = new StringBuffer();
    while (m.find( )) {
        int start = Integer.parseInt(m.group(1));
        int end = Integer.parseInt(m.group(2));
        m.appendReplacement(stringBuffer, getCSV(start, end+1));
    }
    System.out.println(stringBuffer);
}

    Output:

    1 2 3 4 5 6 7 8 9 10 13 14 15 16 17 18 19 20 21 22 23 24 25

    This approach uses a regex matcher to identify every pair of numbers which is in ellipsis (e.g. 4.. 9), and then replaces it with a space separated continuous range from the starting to ending point. Java 8 streams come in handy here, and the getCSV() method generates a string containing the sequence of numbers from the starting and ending input values. Then, we need only iterate over the entire input, and replace each ellipsis using the helper method.

    Demo