How do I avoid the implicit "^" and "$" in Java regular expression matching?

Question

I've been struggling with doing some relatively straightforward regular expression matching in Java 1.4.2. I'm much more comfortable with the Perl way of doing things. Here's what's going on:

I am attempting to match /^<foo>/ from "<foo><bar>"

I try:

Pattern myPattern= Pattern.compile("^<foo>");
Matcher myMatcher= myPattern.matcher("<foo><bar>");
System.out.println(myMatcher.matches());

And I get "false"

I am used to saying:

print "<foo><bar>" =~ /^<foo>/;

which does indeed return true.

After much searching and experimentation, I discovered this which said:

"The String method further optimizes its search criteria by placing an invisible ^ before the pattern and a $ after it."

When I tried:

Pattern myPattern= Pattern.compile("^<foo>.*");
Matcher myMatcher= myPattern.matcher("<foo><bar>");
System.out.println(myMatcher.matches());

then it returns the expected true. I do not want that pattern though. The terminating .* should not be necessary.

Then I discovered the Matcher.useAnchoringBounds(boolean) method. I thought that expressly telling it to not use the anchoring bounds would work. It did not. I tried issuing a

myMatcher.reset();

in case I needed to flush it after turning the attribute off. No luck. Subsequently calling .matches() still returns false.

What have I overlooked?

Edit: Well, that was easy, thanks.

Answer 1

Use the Matcher find method (instead of the matches method)

Answer 2

Matcher.useAnchoringBounds() was added in JDK1.5 so if you are using 1.4, I'm not sure that it would help you even if it did work (notice the @since 1.5 in the Javadocs).

The Javadocs for Matcher also state that the match() method:

Attempts to match the entire region against the pattern.

(emphasis mine)

Which explains why you only got .matches() == true when you changed the pattern to end with .*.

To match against the region starting at the beginning, but not necessarily requiring that the entire region be matched, use either the find() or lookingAt() methods.