Java Regular Expressions
External
Internal
Overview
Regular expressions can be used in Java via the String API or java.util.regex API.
java.util.regex API
The default sequence for using regular expressions consists in building a Pattern instance, which then can be matched against multiple strings by applying it via Matcher instances. The Pattern instance contains a compiled representation of the regular expression. The Matcher uses the Pattern, but encapsulates all the state required to perform matching against a String, so the Pattern can be shared by multiple Matchers. The Matcher instances are not thread safe, see Concurrent Usage Considerations below.
Once built, a Matcher instance can be used to match or find.
Marcher.matches()
matches() vs find()
Working code is available here:
The Difference between matches() and find()
java.langString API
String s = "...";
s.matches(...);
While convenient in some cases, the String API also delegates to the java.util.regex API via the Pattern.matches() call.
Concurrent Usage Considerations
Matcher instances are NOT thread safe, create a matcher per thread