Java regular expression OR operator

Question

This may be a dumb question, but I couldn't find it anywhere:

How can I use the java OR regular expression operator (|) without parentheses?

e.g: Tel|Phone|Fax

yeah, should work. cletus, danben, and myself agree. also, @danben - my name is Dan Beam, lol, so close! — Dan Beam
– Dan Beam, Commented Jan 9, 2010 at 0:49

cletus · Accepted Answer · 2010-01-09 00:57:04Z

179

You can just use the pipe on its own:

"string1|string2"

for example:

String s = "string1, string2, string3";
System.out.println(s.replaceAll("string1|string2", "blah"));

Output:

blah, blah, string3

The main reason to use parentheses is to limit the scope of the alternatives:

String s = "string1, string2, string3";
System.out.println(s.replaceAll("string(1|2)", "blah"));

has the same output. but if you just do this:

String s = "string1, string2, string3";
System.out.println(s.replaceAll("string1|2", "blah"));

you get:

blah, stringblah, string3

because you've said "string1" or "2".

If you don't want to capture that part of the expression use ?::

String s = "string1, string2, string3";
System.out.println(s.replaceAll("string(?:1|2)", "blah"));

answered Jan 9, 2010 at 0:46

cletus

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2 Comments

What if i need to delimit these strings from other pieces of the regex that are also strings? e.g. eee(ff|gg)eee Do I have to use parentheses?

Ah nevermind. Your update fixes it. The last example is what I was looking for. Thanks!