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javaregexstringreplaceampersand

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 &
Solution

  • 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;)", "&");