In perl
s/(.)1+/$1/g;
Does the trick, I assume if java has perl compatible regexps it should work too.
Edit: Here is what it means
s {
(.) # match any charater ( and capture it )
1 # if it is followed by itself
+ # One or more times
}{$1}gx; # And replace the whole things by the first captured character (with g modifier to replace all occurences)
Edit: As others have pointed out, the syntax in Java would become
original.replaceAll("(.)\1+", "$1");
remember to escape the 1
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