Java Pattern RegEx for Conditional Removal of Whitespaces

Question

I have searched for an answer for a couple of hours now and still nothing comes close to solving a specific programming predicament. This is neither for school or work. I'm developing an app that needs to perform pre-defined data cleansing tasks based on regular expressions. One specific expression that I'm having issues with is that of removing whitespace characters between a word and a number. Below are example requirements:

word 123           ==> word123
123 word           ==> 123word
world 123 wide     ==> word123wide
world wide 123     ==> world wide123
world wide 123 456 ==> world wide123 456

RegEx lookaround seems to be the right approach but still can't figure out how to apply the expression for phrases having more than 2 word blocks.

Thanks in advance.

Mena · Accepted Answer · 2013-12-09 20:20:06Z

4

Use a combination of lookarounds and alternance between two Patterns, as such:

//                | preceded by digit
//                |      | one whitespace
//                |      |   | followed by non-digit
//                |      |   |      | OR
//                |      |   |      | | preceded by non-digit
//                |      |   |      | |      | one whitespace
//                |      |   |      | |      |   | followed by digit
String pattern = "(?<=\\d)\\s(?=\\D)|(?<=\\D)\\s(?=\\d)";
// test Strings
String test0 = "word 123";
String test1 = "123 word";
String test2 = "world 123 wide";
String test3 = "world wide 123";
String test4 = "world wide 123 456";
// testing output: replace all found matches
// (e.g. one per String in this case)
// with empty
System.out.println(test0.replaceAll(pattern, ""));
System.out.println(test1.replaceAll(pattern, ""));
System.out.println(test2.replaceAll(pattern, ""));
System.out.println(test3.replaceAll(pattern, ""));
System.out.println(test4.replaceAll(pattern, ""));

Output:

word123
123word
world123wide
world wide123
world wide123 456

answered Dec 9, 2013 at 20:20

Mena

48.6k11 gold badges90 silver badges110 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Bohemian Over a year ago

+1 but I would probably use \\s+ rather than just \\s: "whitespace" usually means any number of whitespace characters

RyPope Over a year ago

@Mena - A true regex wizard

Mena Over a year ago

@Bohemian good point. I added "one whitespace" in my comments, but it could easily be replaced by any number thereof :)

Dan W Over a year ago

Love the "drop-down" helper explanations.

Jay Over a year ago

That was quick! Now I know why I can't seem to make it work for phrases having more than 2 word blocks. I was missing the 2nd lookaround expression. Thank you so much.

|

Collectives™ on Stack Overflow

Java Pattern RegEx for Conditional Removal of Whitespaces

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related