Ufdjrw

I've a path dirntsubdir1ntsubdir2nttfile.ext that I want to process one segment at a time. For each segment, I want to know how many tabs precede it, and I want to have the rest of the path intact. For the given example

Iteration 1:

Preceding tabs: 0
Segment: dir
Rest: ntsubdir1ntsubdir2nttfile.ext

Iteration 2:

Preceding tabs: 1
Segment: subdir1
Rest: ntsubdir2nttfile.ext

Iteration 3:

Preceding tabs: 1
Segment: subdir2
Rest: nttfile.ext

Iteration 4:

Preceding tabs: 2
Segment: file.ext
Rest: ""

The pattern I came up with is ((?<=\R)\h*)(\H+). However, that is giving me tsubdir1n as the first match. What am I doing wrong?

Since all sections are separated by line separator n you can simply use .+ to match them since by default dot . can't match line separators, so you are sure that it will stop before n (or any other line separator like r).

You can also add some groups to separate tabs from actual segment like named group (?<tabs>t*) to match zero or more tabs at start of each match.

To print rest of text after match simply substring after index of last matched character (you can obtain it via Matcher#end).

To print string which will contain n and t (not as literals but as pair of backslash and letter) you can either manually replace each "n" with "\n" and "t" with "\t" or use utility class like StringEscapeUtils from org.apache.commons.lang which contains escapeJava method which does it for us.

So your code can look like:

String path = "dirntsubdir1ntsubdir2nttfile.ext";
Pattern p = Pattern.compile("(?<tabs>t*)(?<segment>.+)");//dot can't match line separators
Matcher m = p.matcher(path);
int i = 1;
while(m.find())
 System.out.println("iteration: " + i++);
 System.out.println("Preceding tabs: " + (m.group("tabs").length()));
 System.out.println("Segment: " + m.group("segment"));
 System.out.println("Rest: "+ StringEscapeUtils.escapeJava(path.substring(m.end())));
 System.out.println();

Output:

iteration: 1
Preceding tabs: 0
Segment: dir
Rest: ntsubdir1ntsubdir2nttfile.ext

iteration: 2
Preceding tabs: 1
Segment: subdir1
Rest: ntsubdir2nttfile.ext

iteration: 3
Preceding tabs: 1
Segment: subdir2
Rest: nttfile.ext

iteration: 4
Preceding tabs: 2
Segment: file.ext
Rest: