If i have this String:
String line = "This, is Stack; Overflow.";
And want to split it into the following array of strings:
String[] array = ...
so the array contains this output:
["This",",","is","Stack",";","Overflow","."]
What regex expression should i put into the split() method ?
Just split your input according to the spaces or the boundaries which exists between a word character and a non-word character, vice-versa.
String s = "This, is Stack; Overflow.";
String parts[] = s.split("\\s|(?<=\\w)(?=\\W)");
System.out.println(Arrays.toString(parts));
\s matches any kind of whitespace character, \w matches a word character and \W matches a non-word character.
\s matches a space character.(?<=\\w) Positive look-behind which asserts that the match must be preceded by a word character (a-z, A-Z, 0-9, _). (?=\\W) Positive look-ahead which asserts that the match must be followed by a non-word character(any character other than the word character). So this (?<=\\w)(?=\\W) regex matches only the boundaries not a character.
Thus splitting the input according to the matches spaces and the boundaries will give you the desired output.
OR
String s = "This, is Stack; Overflow.";
String parts[] = s.split("\\s|(?<=\\w)(?=\\W)|(?<=[^\\w\\s])(?=\\w)");
System.out.println(Arrays.toString(parts));
Output:
[This, ,, is, Stack, ;, Overflow, .]
You can do that with this pattern:
\\s+|(?<=\\S)(?=[^\\w\\s])|(?<=[^\\w\\s])\\b
it trims whitespaces and deals with consecutive special characters, example:
With ;This, is Stack; ;; Overflow.
you obtain: [";", "This", ",", "is", "Stack", ";", ";", ";", "Overflow", "."]
But obviously, the more efficient way is to not use the split method but the find method with this pattern:
\\w+|[^\\w\\s]
