In Java (JDK 11), consider the following string:

String hello = "333 444 5qwerty5 006 -7";

I am trying to come up with a RegEx that will split anything that isn't a digit, whilst keeping the separators except space. So in the above example, I would like to end up with the following array:

["333" , " " , "444" , "5" , "q" , "w" , "e" , "r" , "t" , "y" , "5" , "006" , "-7"]

Do note the leading zeroes in 006, and -7. The code I am using is the following:

String[] splited = s.split("((?<=[^0-9] )|(?=[^0-9] )|(\\s ))");

However, I can see that my array is keeping spaces. I can't for the life of me figure my mistake. Any thoughts?

EDIT: Turns out the requirement is even more complex than I thought:

["333 444" , "5" , "q" , "w" , "e" , "r" , "t" , "y" , "5" , "006" , "-7"]

So if there is no space between an integer and operators - * / % ^, then do not split them. I have issues implementing this rule along with the fact that leading zeroes and negative numbers should not be split.

CodePudding user response：

Instead of using split, you could also match all the parts:

-?\d |\S

The pattern matches:

• -? Optionally match a hyphen
• \d Match 1 digits
• | Or
• \S Match a single non whitespace char

See a regex demo and a Java demo.

Example

String regex = "-?\\d |\\S";
String string = "333 444 5qwerty5 006 -7";

List<String> allMatches = new ArrayList<String>();

Matcher m = Pattern.compile(regex).matcher(string);
while (m.find()) {
    allMatches.add(m.group());
}

System.out.println(Arrays.toString(allMatches.toArray()));

Output

[333,  , 444, 5, q, w, e, r, t, y, 5, 006, -7]

CodePudding user response：

This works for your example:

String[] split = hello.split("(?<=\\d)(?=\\D) *|(?<=[^\\d -])(?=[\\d-])|(?<=[\\d-])(?=[^\\d -])|(?<=[^\\d -])(?=[^\\d -])");

The important parts are:

• Using [\\d-] instead of \d so minus signs are treated as "digits"
• Generally using [^\d -] instead of \D to prevent empty split elements at word ends
• Splitting after digits, but only if a non-digit follows
• Adding * to capture ("delete") spaces when splitting
• Splitting between non-digits

Test code:

String hello = "333 444 5qwerty5 006 -7";
String[] split = hello.split("(?<=\\d)(?=\\D) *|(?<=[^\\d -])(?=[\\d-])|(?<=[\\d-])(?=[^\\d -])|(?<=[^\\d -])(?=[^\\d -])");
System.out.println(Arrays.toString(split));

Output:

[333,  , 444, 5, q, w, e, r, t, y, 5, 006, -7]