String replace regex [closed]

Question

So I'm struggling with this one a little bit. When I'm pulling strings from somewhere It's decided to add spaces in between every character.

I just need a quick regex to:

• Replace single spaces with no space
• replace triple spaces with 1 space (since " " turns into "   " with the added spaces).

Can someone help with this regex? I know how to do this for a single / multiple spaces, but not turning x number of spaces into 1 space.

Answer 1

It is a little tricky, but here is a single regex solution:

// becomes "test string"
"t e s t   s t r i n g".replaceAll("( )  | ", "$1");

Example: http://ideone.com/O6DSk

This works because if a triple space is matched, one of the spaces will be saved in capture group 1, but if a single space is matched capture group 1 is empty. When we replace the match by the contents of the group it will turn three spaces into one and remove single spaces.

Answer 2

s = s.replaceAll("\\s{3}", " ");  // Replace 3 spaces with one.

I assume you know to figure out, replacing single space with no space.

• {n} matches exactly n spaces.
• {0,n} matches 0 to n spaces.
• {4,} matches 4 or more spaces.

To replace both single space with no space and 3 spaces with 1 space, you can use the below regex: -

s = "He llo   World";
s = s.replaceAll("(\\S)\\s{1}(\\S)", "$1$2").replaceAll("\\s{3}", " ");

System.out.println(s);

Ouput: -

Hello World

Order matters here. Because, 3 spaces will be converted to single space with the 2nd regex. If we use it before the 1st one, then eventually it will be replaced by no-space.

(\\S)\\s{1}(\\S) -> \\S is to ensure that only single space is replaced. \\S represents non-space character. If you don't have it, it will replace all the space character with no-space.