Dynamic incrementation of all numbers within a String

Question

Is there any Java solution of replacing a digit in a String other than getting the digit using a matcher, increment it by one and replace it?

"REPEAT_FOR_4" will return "REPEAT_FOR_5" "REPEAT_FOR_10" will return "REPEAT_FOR_11"

I would like to do it in one line with regex and replace, not by recomposing the String as "REPEAT_FOR_" and add the number after incrementation. Thank you!

Later edit: I would like to know how to replace a number with the following one in a String.

Technically, you can't "replace" anything in a `String`, because objects of `String` are immutable. But you can create a new `String` containing the old prefix plus Integer.valueOf(suffix) + 1. — Smutje, Oct 13 '16 at 14:10
Yes, I know. I will update my question. Generate a new String :) — sonya, Oct 13 '16 at 14:10
You could use an IntStream, map it to an Integer, then produce a list of strings in one line of code. — mttdbrd, Oct 13 '16 at 14:10
In this case, regex will only make the code longer, not shorter. — RealSkeptic, Oct 13 '16 at 14:26
What is the pattern of the String? The number is always at the end, always present, The splitter is `_`? Could you enumerate more condition ? — AxelH, Oct 13 '16 at 14:33
No, this only an example. I would like to know solutions for replace any number in a String with the following one. — sonya, Oct 13 '16 at 14:41
@rianna, then update your example. This is not clear for me (and others too). You need to specify a pattern, or patterns of String. (or a number anywhere...) — AxelH, Oct 13 '16 at 14:43
don't be sorry , it was a good question though :) , you can try this too http://stackoverflow.com/questions/1453365/increment-digit-value-in-string , , plus the below given answers are also great examples too — Pavneet_Singh, Oct 13 '16 at 15:10
Revising my comment from yesterday to use iterate() instead of generate().This does not satisfy the requirement of not recomposing the String, but it will generate any number of Strings in one line: List strings = IntStream.iterate(0, x -> ++x).limit(100) .mapToObj(x -> "REPEAT_FOR_" + Integer.toString(x)) .collect(Collectors.toList()); — mttdbrd, Oct 14 '16 at 16:22

Eddie Martinez · Answer 1 · 2016-10-13T14:26:10.293

0

I didn't use regex but here is the solution in one line. Considering your string remains the same.

public String getIncrementedString (String str){
return ("REPEAT_FOR_" + (Character.getNumericValue(str.charAt(11))+1));
}

edited Oct 13 '16 at 14:26

answered Oct 13 '16 at 14:23

Eddie Martinez

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OP says: **not by recomposing the String as "REPEAT_FOR_" and add the number after incrementation** – RealSkeptic Oct 13 '16 at 14:25
but it seems his issue was he wanted to do it in one line. – Eddie Martinez Oct 13 '16 at 14:26

Seek Addo · Answer 2 · 2016-10-13T14:51:04.497

You can try this.

String ss = "REPEAT_FOR_4";
int vd = Integer.valueOf(ss.substring(ss.length() - 1));
String nss = ss.replaceAll("\\d",String.valueOf(vd+1));

System.out.println(nss);

output:

REPEAT_FOR_5

with regex: if the digit is not at the end of the string.

    String ss = "REPEAT_5_FOR_ME";
    Pattern p = Pattern.compile("\\d+");
    Matcher m = p.matcher(ss);
    m.find();
    String strb = m.group();
    int vd = Integer.valueOf(strb);
    String nss = ss.replaceAll("\\d",String.valueOf(vd+1));

    System.out.println(nss);

output:

REPEAT_6_FOR_ME

Base on the issue raised in the comments comments i think this solution with regex will help.

public static String convStr(String str){
    Pattern p = Pattern.compile("\\d+");
    Matcher m = p.matcher(str);
    m.find();
    String strb = m.group();
    int vd = Integer.valueOf(strb);
    return str.replaceAll("\\d",String.valueOf(vd+1));
  }

But if the number is not on the end of the string, it will not work. I came up to this solution: String nrToBeReplaced = CharMatcher.DIGIT.retainFrom(value); int nextNr = Integer.valueOf(nrToBeReplaced) + 1; return value.replaceAll(value, String.valueOf(nextNr)); — sonya, Oct 13 '16 at 14:38
@rianna i have updated my answer with regex and it solves the issue you raised — Seek Addo, Oct 13 '16 at 14:52

score 0 · Answer 3 · answered Oct 13 '16 at 14:43

Yes of course it's possible. using regex Pattern and Matcher, here's what you will need to do:

    String str = "REPEAT_FOR_4";
    Pattern p = Pattern.compile("([0-9]+)");
    Matcher m = p.matcher(str);
    StringBuffer s = new StringBuffer();
    while (m.find())
        m.appendReplacement(s, String.valueOf(1+ Integer.parseInt(m.group(1))));
    String updated = s.toString();
    System.out.println(updated);

This is a working Example that returns REPEAT_FOR_5 as output.

Dynamic incrementation of all numbers within a String

3 Answers3