Regular Expressions - Introduction to Java Programming: Comprehensive Version - page 1279

T ABLE H.1

Frequently Used Regular Expressions
Regular Expression Matches Example

x a specified character x Java matches Java

. any single character Java matches J..a

(ab|cd) ab or cd ten matches t(en|im)

[abc] a, b, or c Java matches Ja[uvwx]a

[^abc] any character except

a, b, or c

Java matches Ja[^ars]a

[a-z] a through z Java matches [A-M]av[a-d]

[^a-z] any character except

a through z

Java matches Jav[^b-d]

[a-e[m-p]] a through e or

m through p

Java matches [A-G[I-M]]av[a-d]

[a-e&&[c-p]] intersection of a-e

with c-p

Java matches [A-P&&[I-M]]av[a-d]

\d a digit, same as [0-9] Java2 matches "Java[\\d]"

\D a non-digit $Java matches "[\\D][\\D]ava"

\w a word character Java1 matches "[\\w]ava[\\w]"

\W a non-word character $Java matches "[\\W][\\w]ava"

\s a whitespace character "Java 2" matches "Java\\s2"

\S a non-whitespace char Java matches "[\\S]ava"

p * zero or more

occurrences of pattern p

aaaabb matches "a*bb"
ababab matches "(ab)*"

p + one or more occurrences

of pattern p

a matches "a+b*"
able matches "(ab)+.*"

p ? zero or one occurrence of

pattern p

Java matches "J?Java"
Java matches "J?ava"

p {n} exactly n occurrences of

pattern p

Java matches "Ja{1}.*"
Java does not match ".{2}"

p {n,} at least n occurrences of

pattern p

aaaa matches "a{1,}"
a does not match "a{2,}"

p {n,m} between n and m occur-

rences (inclusive)

aaaa matches "a{1,9}"
abb does not match "a{2,9}bb"

Note
A word character is any letter, digit, or the underscore character. So \w is the same
as [a-z[A-Z][0-9]_] or simply [a-zA-Z0-9_] , and \W is the same as
[^a-zA-Z0-9_] .

Note
The last six entries * , + , ? , {n} , {n,} , and {n, m} in Table H.1 are called quantifiers
that specify how many times the pattern before a quantifier may repeat. For example, A*
matches zero or more A 's, A+ matches one or more A 's, A? matches zero or one A 's, A{3}
matches exactly AAA , A{3,} matches at least three A 's, and A{3,6} matches between
3 and 6 A 's. * is the same as {0,} , + is the same as {1,} , and ? is the same as {0,1} .

quantifier