Question

In Java I want to insert a space after a String but only if the character after the comma is succeeded by a digit or letter. I am hoping to use the replaceAll method which uses regular expressions as a parameter. So far I have the following:

String s1="428.0,chf";
s1 = s1.replaceAll(",(\\d|\\w)",", ");   

This code does successfully distinguish between the String above and one where there is already a space after the comma. My problem is that I can’t figure out how to write the expression so that the space is inserted. The code above will replace the c in the String shown above with a space. This is not what I want.

s1 should look like this after executing the replaceAll: "428.0 chf"

Answer 1

Try this, and note that $1 refers to your matched grouping:

s1.replaceAll(",(\\d|\\w)"," $1");

Note that String.replaceAll() works in the same way as a Matcher.replaceAll(). From the doc:

The replacement string may contain references to captured subsequences