Remove all empty lines

Question

I thought that wasn't that hard to do, but I want to remove all empty lines (or lines just containing blanks and tabs in Java) with String.replaceAll.

My regex looks like this:

s = s.replaceAll ("^[ |\t]*\n$", ""); 

But it doesn't work.

I looked around, but only found regexes for removing empty lines without blanks or tabs.

Answer 1

Try this:

String text = "line 1\n\nline 3\n\n\nline 5"; String adjusted = text.replaceAll("(?m)^[ \t]*\r?\n", ""); // ... 

Note that the regex [ |\t] matches a space, a tab or a pipe char!

EDIT

B.t.w., the regex (?m)^\s+$ would also do the trick.

Answer 2

I don't know the syntax for regular expressions in Java, but /^\s*$[\n\r]{1,}/gm is the regex you're looking for.

You probably write it like this in Java:

s = s.replaceAll("(?m)^\\s*$[\n\r]{1,}", ""); 

I tested it with JavaScript and it works fine.