Regex pattern to convert comma separated string to dot separated one

Question

I want to convert an long array values to a specific format of string.

for e.g. longArray = {0,1,2,3} to be converted as string 0.1.2.3

I can do Arrays.toString(longArray) which will return [0, 1, 2, 3].

Now this string [0,1,2,3] has to be converted into 0.1.2.3

I have used this code which works but would like to see if this code can be improved

String convertedString = Arrays.toString(longArray).replaceAll(",",".").replaceAll("[\\[,\\],\\s]", "");

I have to mention that i am on Java 7 so can't use any Java 8 features like streams Best Regards,

Saurav

Most languages have a join function. Use . as the character. If java doesn't, just loop through the array.. make your own string. — user557597
– user557597, Commented Jan 17, 2018 at 16:08
concision-wise, given it's Java, that seems to be as good as it gets (if you don't want to include 3rd party libraries), though you could use a static import — DPM
– DPM, Commented Jan 17, 2018 at 16:08
Possible duplicate of Java: join array of primitives with separator — ctwheels
– ctwheels, Commented Jan 17, 2018 at 16:09
The regex character class [] doesn't use comma to separate characters. A character class matching a and b would be [ab], not [a,b]. Also, super minor improvement, the second replaceAll call shortens the text, so flipping the order will leave fewer characters for the other replaceAll call to process: .replaceAll("[\\[\\]\\s]+", "").replaceAll(",",".") (see this comment thread about the + I added). — Andreas
– Andreas, Commented Jan 17, 2018 at 16:23
Arrays.toString(longArray).replace(", ", ".").replaceFirst(".(.*).", "$1"); — Joop Eggen
– Joop Eggen, Commented Jan 17, 2018 at 16:34

Joop Eggen · Accepted Answer · 2018-01-17 16:31:07Z

1

    long[] longArray = {0,1,2,3};
    String s = LongStream.of(longArray)
            .mapToObj(Long::toString)
            .collect(Collectors.joining("."));

Array of longs to stream of longs, every long mapped to a String with Long.toString(long) and then joined with a delimiter ..

Originally I has String::valueOf instead of Long.toString. Thanks to @Andreas for a slightly better style.

edited Jan 17, 2018 at 16:31

answered Jan 17, 2018 at 16:24

Joop Eggen

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Joop Eggen Over a year ago

@Andreas Or Long::toString(long).

GalAbra · Accepted Answer · 2018-01-17 16:35:04Z

0

Not much shorter, but I think the regular expressions make it look more elegant:

String convertedString = Arrays.toString(longArray)
.replaceAll("^.|.$", "");
.replaceAll("[^0-9]+",".")

Remove first and last character.
Replace all non-numeric strings with dots.

edited Jan 17, 2018 at 16:35

answered Jan 17, 2018 at 16:27

GalAbra

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4 Comments

saurav Over a year ago

seems almost same as my proposed solution...any performance improvement with your solution by using the negate operator ?

Andreas Over a year ago

You do know that . does match a period, right? It matches any character, so it would be safer to escape it, i.e. "^\\.|\\.$"

GalAbra Over a year ago

Just the use of the +, to include all the strings, not only individual characters

GalAbra Over a year ago

@Andreas I intentionally want to remove the first and the last characters

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