Find String Within a String

I have a string like:

1,7,8 or

7,8,11

If I use the indexOf("1") it will find a match in both strings. How can I make it do an exact match?

You just have to be more specific about what an exact match would entail. You could use a regular expression which said something like

a comma or the beginning of the string, followed by
the search target, followed by
a comma or the end of the string.

What if my string is:

11,

indexOf(",11,") will not work.

no, but building a regular expression and and using matches() will:
myStringOfNumbers.matches(".*?(\\A|\\,)" + myNumber + "(\\z|\\,).*+");

yet simpler, try
("," + myStringOfNumbers + ",").indexOf("," + myNumber + ",")

O'Reilly has entire books on writing regular expressions. you may want to check some of them out.

part of the art of writing a good regex is understanding what you input can be, as much as what you want to get out of it...

Guido's last post is good for a simple way to do this without regular expressions. However if you find you need a more flexible solution, you may need to come back to regular expressions. Good free tutorials on regular expressions can be found at

http://www.regular-expressions.info/tutorial.html

and

http://java.sun.com/docs/books/tutorial/essential/regex/

Also of interest is the API for the Pattern class.

In this case you can also make use of \b to match a word boundary: "\\b11\\b" will match "11" as long as it's preceded and followed by non-word characters, or the beginning or end of the string.
[ April 30, 2008: Message edited by: Jim Yingst ]