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  • What is regular expression?

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    Regular expression or Regex is an API which is used for pattern matching and it basically defines a search pattern of input.  We can also search, edit or manipulate text or data from regular expression. Let’s suppose if we need to define some constraints on any string(eg: passwords and email validation) then we will use regular-expression.

    Benefit of regex:

    1> Regex are fast for execution

    2> Regex save time

    3> Regex can match just about anything

    4> Searching (and possibly replacing) text in files

    Eg: Search pattern: (text)

            Replace: $text

    The search pattern text will replace from replaced text in a file.


    5> Renaming a hundred files at a time

    Eg: Changing the File Extension:

           Search pattern: ^(.*\.)[^.]+$

           Replace: $1rar

    ^(.*\.)[^.]--> Matches any character after the dot and then replace that string that is extension with rar.


    Java Regex API provides 1 interface and 3 classes in java.util.regex package.


    1. MatchResult interface

    2. Matcher class

    3. Pattern class

    4. PatternSyntaxException class

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