Replacing two EOL chars by one

Xah Lee wrote:

i have a bunch of java files that has spaced-out formatting that i
want to get rid of. I want to replace two end of line characters by
one end of line characters. The files in question is unix, and i’m
also working under unix, so i did:

perl -pi’*~’ -e “s@\n\n@\n@g” *.java

but this to no avail.

after many minutes of checking and rechecking and lots of trial and
error with frustration, i realized that the fucking perl to my
expectations again cannot do this simple fucking thing. Nor can the
unix utility tr. Fucking stupid perl couldn’t do a simple task of
replacing strings.

let me just take this opportunity to explain one shit from the
thousands from perldoc.
[rest of rant snipped]

Five seconds of thinking might have spared you from embarassing yourself
like that (and is certainly more effective than 5 paragraphs of swearing).
You are reading the file line by line. And with each line you are looking
for two consecutive newlines.
Now, how can a single line contain two newlines?

jue