Regular
expressions are powerful tool for text processing. A regular
expression is a sequence of characters that forms a search pattern,
mainly used for pattern matching in strings. Regular Expressions are
used to search, edit, or manipulate text and data. Once you
comfortable in regular expressions, you will find the advantage of
regular expressions.
'java.util.regex'
package provides Classes for matching character sequences against
patterns specified by regular expressions. The regular expression
syntax in the java.util.regex API is most similar to that found in
Perl.
A
Regular expression is composed of two types of characters.
a.
Metacharacters (*, ., ?, ^, $ etc.,) : Metacharacters have special
meaning.
b.
Literals : Normal characters without special meaning.
For
Ex: a*b
a,b
are literals and '*' is the metacharacter. 'a*b' matches strings like
b, ab, aab, aaab, aaaaab etc.,
a*
means 'a' can be repeated zero or more times.
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