P Bose P Bose - 6 months ago 34
Java Question

Java String Replace '&' with & but not & to &

I have a large String in which I have & characters used available in following patterns -

A&B
A & B
A& B
A &B
A&B
A & B
A& B
A &B


I want to replace all the occurrences of & character to
&

While replacing this, I also need to make sure that I do not mistakenly convert an
&
to
&
. How do I do that in a performance savvy way? Do I use regular expression? If yes, please can you help me to pickup the right regular expression to do the above?

I've tried following so far with no joy:

data = data.replace(" & ", "&"); // doesn't replace all &
data = data.replace("&", "&"); // replaces all &, so & becomes &

Answer

You can use a regular expression with a negative lookahead.

The regex string would be &(?!amp;).

Using replaceAll, you would get:

A&B
A & B
A& B
A &B
A&B
A & B
A& B
A &B

So the code for a single string str would be:

str.replaceAll("&(?!amp;)", "&");