Class BackReferenceTest

java.lang.Object

BackReferenceTest

public class BackReferenceTest
extends Object

Constructor Summary

Constructors

Constructor	Description
BackReferenceTest()

Method Summary

Modifier and Type	Method	Description
void	testBackReferenceRegex()	The backReference regex:
void	testNamedBackReferenceRegex()	The namedBackReference regex:

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BackReferenceTest

public BackReferenceTest()

Method Detail

testBackReferenceRegex

public void testBackReferenceRegex()

The backReference regex:

\number

In this case we use the following regex:

(\w)\1

In this test case the backReference matches the expression of the capturing group again. So, with the String "seek" the capturing group, i.e. (\w), matches all the characters but using the backReference matches the same pattern, obtaining the result "ee", because it's the only part of the String that is consecutively equal.

testNamedBackReferenceRegex

public void testNamedBackReferenceRegex()

The namedBackReference regex:

\k<name>

In this case we use the following regex:

(?<char>\w)\k<char>

There are two parts on this regex, first we define a named capturing group, (?<char>\w), and then we define the

namedBackReference, \k<char>.

This is very similar to the backReference regex. The named capturing group matches all the characters but using the namedBackReference the same pattern is matched, obtaining a single result "ee" using the String "seek", because it's the only part of the String that is consecutively equal.