StephanSchrader / readable-regex

Java library for creating readable regular expressions

Readable Regex

This library provides a way to make complex regular expressions in Java code more readable.

The best way to explain what it does to show some examples:

 // Matches a single digit
    RegExBuilder.build(anyDigit()); // "[0-9]"

 // Matches exactly 2 digits
	RegExBuilder.build(exactly(2).of(anyDigit())); // "[0-9]{2}"

 // Matches between 2 and 4 letters
	RegExBuilder.build(between(2,4).of(anyLetter())); // "[a-zA-Z]{2,4}"

Characters that have special meaning within a regular expression are escaped automatically:

 // Matches one or more occurrences of the text 'Ho?'
	RegExBuilder.build(oneOrMore().of("Ho?")); // "(Ho\?)+"
	
 // Matches anything except an opening or closing square bracket, or a backslash
	RegExBuilder.build(
		anyCharacterExcept(
			characters('[', ']','\\')
		)
	); // "[^[\\]\\\\]"

Readability is greatly improved for more complex expressions:

 // More or less validates the format of an email address
 // [_\\-A-Za-z0-9]+(\\.[_\\-A-Za-z0-9]+)*@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*\\.[a-zA-Z]{2,}
    RegExBuilder.build(
	    oneOrMore().of(
		    anyOneOf(
			    characters('_','-'), range('A','Z'), range('a','z'), range('0','9')
			)
    	),
	    zeroOrMore().of(
		    text("."),
			oneOrMore().of(
    			anyOneOf(
	    			characters('_','-'), range('A','Z'), range('a','z'), range('0','9')
		    	)
			)
    	),
	    text("@"),
		oneOrMore().of(
    		anyOneOf(
	    		range('A','Z'), range('a','z'), range('0','9')
		    )
		),
    	zeroOrMore().of(
	    	text("."),
		    oneOrMore().of(
			    anyOneOf(
				    range('A','Z'), range('a','z'), range('0','9')
				)
    		)
	    ),
		text("."),
    	atLeast(2).of(
	    	anyLetter()
		)
    );

All classes in the library are immutable, and therefore instances are re-usable and thread-safe.