How to split a string between letters and digits or between digits and letters

Question

I m trying to work out a way of splitting up a string in java that follows a pattern like so   String a    123abc345def     The results from this should be the following   x 0     123   x 1     abc   x 2     345   x 3     def     However I m completely stumped as to how I can achieve this  Please can someone help me out  I have tried searching online for a similar problem  however it s very difficult to phrase it correctly in a search   Please note  The number of letters  amp  numbers may vary  e g  There could be a string like so  1234a5bcdef

User · Answer

If you are looking for solution without using Java String functionality (i.e. split, match, etc.) then the following should help:

List<String> splitString(String string) {
        List<String> list = new ArrayList<String>();
        String token = "";
        char curr;
        for (int e = 0; e < string.length() + 1; e++) {
            if (e == 0)
                curr = string.charAt(0);
            else {
                curr = string.charAt(--e);
            }

            if (isNumber(curr)) {
                while (e < string.length() && isNumber(string.charAt(e))) {
                    token += string.charAt(e++);
                }
                list.add(token);
                token = "";
            } else {
                while (e < string.length() && !isNumber(string.charAt(e))) {
                    token += string.charAt(e++);
                }
                list.add(token);
                token = "";
            }

        }

        return list;
    }

boolean isNumber(char c) {
        return c >= '0' && c <= '9';
    }

This solution will split numbers and 'words', where 'words' are strings that don't contain numbers. However, if you like to have only 'words' containing English letters then you can easily modify it by adding more conditions (like isNumber method call) depending on your requirements (for example you may wish to skip words that contain non English letters). Also note that the splitString method returns ArrayList which later can be converted to String array.

User · Answer

Wouldn t this  d  D   do the job instead of the cumbersome      lt    D      d     lt    d      D

User · Answer

Didn t use Java for ages  so just some pseudo code  that should help get you started  faster for me than looking up everything         string a    123abc345def    string   result   while a Length  gt  0           string part        if  part   a Match   d     Length     match digits                    else if  part   a Match   a     Length     match letters                    else            break     something invalid - neither digit nor letter       result append part         a   a SubStr part Length - 1      remove the part we ve found

User · Answer

How about   private List lt String gt  Parse String str        List lt String gt  output   new ArrayList lt String gt         Matcher match   Pattern compile   0-9    a-z    A-Z     matcher str       while  match find              output add match group               return output

User · Answer

You could try to split on    lt   D     d     lt   d     D   like   str split     lt    D      d     lt    d      D       It matches positions between a number and not-a-number  in any order        lt   D     d  - matches a position between a non-digit   D  and a digit   d     lt   d     D  - matches a position between a digit and a non-digit

User · Answer

You can try this   Pattern p   Pattern compile   a-z     d     Matcher m   p matcher  123abc345def    ArrayList lt String gt  allMatches   new ArrayList lt  gt     while  m find          allMatches add m group         The result  allMatches  will be     123    abc    345    def

User · Answer

Use two different patterns   0-9   and  a-zA-Z   and split twice by each of them

User · Answer

I was doing this sort of thing for mission critical code  Like every fraction of a second counts because I need to process 180k entries in an unnoticeable amount of time  So I skipped the regex and split altogether and allowed for inline processing of each element  though adding them to an ArrayList lt String gt  would be fine   If you want to do this exact thing but need it to be something like 20x faster     void parseGroups String text        int last   0      int state   0      for  int i   0  s   text length    i  lt  s  i              switch  text charAt i                 case  0               case  1               case  2               case  3               case  4               case  5               case  6               case  7               case  8               case  9                   if  state    2                        processElement text substring last  i                        last   i                                    state   1                  break              default                  if  state    1                        processElement text substring last  i                        last   i                                    state   2                  break                      processElement text substring last

[java] How to split a string between letters and digits (or between digits and letters)?

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