在多个字符上拆分字符串

Question

I want to split a sentence on one of the many characters (listed below). My regex is able to split based on most of the characters but not on '[', ']' (opening and closing square brackets). If I change the string SPECIAL_CHARACTERS_REGEX to [ :;'=\\\\()!-\\\\[\\\\]] , it starts to split on integers in the string rather than splitting the square brackets instead. How can I make the regex split on square brackets rather than integers ('[]' denotes all integers).

Another related question, is there a way to also split numbers from string? Eg 9pm should be split into 9 and pm .

This:

private static final String SPECIAL_CHARACTERS_REGEX = "[ :;'=\\()!-]";
String rawMessage = "let's meet tomorrow at 9:30p? 7-8pm? i=you go (no Go!) [to do !]"
String[] tokens = rawMessage.split(SPECIAL_CHARACTERS_REGEX);

Gives:

Input: let's meet tomorrow at 9:30p? 7-8pm? i=you go (no Go!) [to do !]
output: [let, s, meet, tomorrow, at, 9, 30p?, 7, 8pm?, i, you, go, , no, Go, , , [to, do, , ]]

And,

This:

private static final String SPECIAL_CHARACTERS_REGEX = "[ :;'=\\()!-\\[\\]]";
String rawMessage = "let's meet tomorrow at 9:30p? 7-8pm? i=you go (no Go!) [to do !]"
String[] tokens = rawMessage.split(SPECIAL_CHARACTERS_REGEX);

Gives:
let's meet tomorrow at 9:30p? 7-8pm? i=you go (no Go!) [to do !]
[let, s, meet, tomorrow, at, , , , , p, , , , , pm, , i, you, go, , no, , o, , , , to, do]

Expected output:

{"let", "s", "meet", "tomorrow", "at", "9", "30", "p", "7", "8", "pm", "i", "you", "go", "no", "Go", "to", "do"}

Answer 1

Put the dash at the end (or beginning or escape it) because otherwise, it will be treated as a range of characters:

[ :;'=\\()!\\[\\]-]

Your original regex was matching all characters between ! and [ which includes numbers, block letters and a bunch of other symbols such as ( , ) and so on.

To get the result you expect, you might use something like this:

[ ?:;'=\\()!\\[\\]-]+|(?<=\\d)(?=\\D)

(?<=\\d)(?=\\D) is to separate digits and non-digits (or you might also want to use [0-9] and [^0-9] which should be a little more efficient/fast)

ideone demo

Answer 2

If you leave the dash in the middle of the character class, you need to escape it also.

However, avoid this by placing it at the beginning or end of your character class. Also you don't need to escape () here, and you possibly want to use a quantifier, either * or + after your character class.

Update : To get your expected results, you could do.

private static final String SPECIAL_CHARACTERS_REGEX = "[ :;'?=()!\\[\\]-]+|(?<=\\d)(?=\\D)";
String rawMessage = "let's meet tomorrow at 9:30p? 7-8pm? i=you go (no Go!) [to do !]";
String[] tokens = rawMessage.split(SPECIAL_CHARACTERS_REGEX);
System.out.println(Arrays.toString(tokens));

Regular expression:

[ :;'?=()!\[\]-]+    any character of: ' ', ':', ';', ''', '?',
                       '=', '(', ')', '!', '\[', '\]', '-' (1 or more times)
 |                   OR
  (?<=               look behind to see if there is:
   \d                digits (0-9)
  )                  end of look-behind
   (?=               look ahead to see if there is:
    \D               non-digits (all but 0-9)
   )                 end of look-ahead

See Working demo

Output

[let, s, meet, tomorrow, at, 9, 30, p, 7, 8, pm, i, you, go, no, Go, to, do]

Answer 3

Using this in the regex will split at any point where a digit is followed by a letter:

(?<=\\d)(?=[A-Za-z])

I've tested using just the above in the pattern. To add it to what you already have, use | in your regex to split on either the above or what you already have:

String[] parts = s.split("[ :;'=()!\\[\\]-]+|(?<=\\d)(?=[A-Za-z])");

(using hwnd's answer). ?<= is a lookbehind, which matches if the pattern just behind a point matches, and ?= is a lookahead, which matches if the pattern just after a point matches.

Answer 4

First introduce space between alpha numeric combinations such as 8pm, then split based the special characters with escape sequence for '[' and ']' :

String rawMessage  = "let's meet tomorrow at 9:30pm 7-8pm? i=you go (no Go!) [to do !]";
String rawMessage2 = rawMessage.replaceAll("(?<=[0-9])(?=[a-zA-Z])", " ");
String[] tokens  = rawMessage2.split("[ :;'=()!\\[\\]]+");