Java Reference
In-Depth Information
Using regexes in Java: Test for a Pattern
Problem
You're ready to get started using regular expression processing to beef up your Java code by
testing to see if a given pattern can match in a given string.
Solution
Use the Java Regular Expressions Package,
java.util.regex
.
Discussion
The good news is that the Java API for regexes is actually easy to use. If all you need is to
find out whether a given regex matches a string, you can use the convenient
boolean
matches()
method of the
String
class, which accepts a regex pattern in
String
form as its
argument:
iif
(
inputString
.
matches
(
stringRegexPattern
)) {
// it matched... do something with it...
}
This is, however, a convenience routine, and convenience always comes at a price. If the
regex is going to be used more than once or twice in a program, it is more efficient to con-
struct and use a
Pattern
and its
Matcher
(s). A complete program constructing a
Pattern
and using it to
match
is shown here:
public
public class
class
RESimple
RESimple
{
public
public static
void
main
(
String
[]
argv
) {
String pattern
=
"^Q[^u]\\d+\\."
;
String
[]
input
= {
"QA777. is the next flight. It is on time."
,
"Quack, Quack, Quack!"
static
void
};
Pattern p
=
Pattern
.
compile
(
pattern
);
for
for
(
String in
:
input
) {
boolean
boolean
found
=
p
.
matcher
(
in
).
lookingAt
();
