Regular Expressions - Introduction to Java Programming: Comprehensive Version - page 1280

Caution
Do not use spaces in the repeat quantifiers. For example, A{3,6} cannot be written as
A{3, 6} with a space after the comma.
Note
You may use parentheses to group patterns. For example, (ab){3} matches ababab ,
but ab{3} matches abbb .
Let us use several examples to demonstrate how to construct regular expressions.
Example 1
The pattern for social security numbers is xxx-xx-xxxx , where x is a digit. A regular
expression for social security numbers can be described as
[\\d]{ 3 }-[\\d]{ 2 }-[\\d]{ 4 }
For example,
"111-22-3333".matches("[\\d]{3}-[\\d]{2}-[\\d]{4}") returns true .
"11-22-3333".matches("[\\d]{3}-[\\d]{2}-[\\d]{4}") returns false .
Example 2
An even number ends with digits 0 , 2 , 4 , 6 , or 8. The pattern for even numbers can be
described as
[\\d]*[ 02468 ]
For example,
"123".matches("[\\d]*[02468]") returns false .
"122".matches("[\\d]*[02468]") returns true .
Example 3
The pattern for telephone numbers is (xxx) xxx-xxxx , where x is a digit and the first
digit cannot be zero. A regular expression for telephone numbers can be described as
\\([ 1 - 9 ][\\d]{ 2 }\\) [\\d]{ 3 }-[\\d]{ 4 }
Note that the parentheses symbols ( and ) are special characters in a regular expression for
grouping patterns. To represent a literal ( or ) in a regular expression, you have to use \\(
and \\) .
For example,
"[phone]".matches("\\([1-9][\\d]{2}\\) [\\d]{3}-[\\d]{4}")
returns true .
"921-2728".matches("\\([1-9][\\d]{2}\\) [\\d]{3}-[\\d]{4}")
returns false .
Example 4
Suppose the last name consists of at most 25 letters and the first letter is in uppercase. The
pattern for a last name can be described as
[A-Z][a-zA-Z]{ 1 , 24 }
Note that you cannot have arbitrary whitespace in a regular expression. For example, [A-Z]
[a-zA-Z]{ 1, 24 } would be wrong.