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JAVA RegEx

Manish Shrivastava

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Recap

A regular expression-- a pattern thatdescribes or atches a set o! strings

E"g" ca#trn$

Matched text% chun& o! text 'hichatches the regular expression" E"g" ca[trn] matches car, can, cat

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Recap

MetacharactersMetacharacters -$^ . \ [] \( \) + ?

SetsSets [aeiou] andand#bcd!gh(&lnp)rstv'x*+$

Negation using (^) e.g.Negation using (^) e.g. [^a^!]

"e#eated match- using"e#eated match- using andand+ %.g. a or[a-&]

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iport (ava"util"regex"

2h* this ac&age3

2hat it contains3

4o' to use this ac&age3

2hat this ac&age can do3

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2h* this ac&age

Ever*thing in Java should be anob(ect o! soe class"

Regular expressions are aniportant part o! an* applications

5ote Regex ac&age 'as onl* introduceda!ter J781"9

Regular expressions (RegEx) tend to

be easier to write than they are to read

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2hat it contains

,he ac&age denes : classes attern% ;A regular expression, specifed

as a string, must frst be compiled intoan instance o this class

Matcher- An engine that per!ors atch

operations on a character se)uenceb*interpreting a attern

http://java.sun.com/j2se/1.4.2/docs/api/java/lang/CharSequence.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/CharSequence.html

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4o' to use (ava"util"regex

Step 1

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2hat can it do

Match RegularExpressions

?7uh@

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Demo

ut ho'3

copile regular expression into an instance o!attern using attern"copile(regex) Eg" attern pat B attern"copile?;#ab$cdC@=

Dse the resulting pattern to create a Matcherob(ect using pattern-naeF"atcher(input) Eg" Matcher atcher B pat"atcher?CaccccdC@=

Gind i! the pattern HpatI atched

Eg" boolean isMatch B atcher"atches?@=All this can also be done b* boolean isMatch B attern"atches?;#ab$cdC>

;accccdC@=

http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.html

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7eep 2aters

oth attern and Matcher classesprovide various !unctions

Most o! the coon operationsare provided as !unctions

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attern Gunctions

static atterncompile?Stringregex@.opiles the given regular

expression into a pattern

Matchermatcher?.harSe)uence

input@.reates a atcher that 'ill atchthe given input against this pattern"

http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/CharSequence.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/CharSequence.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.html

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Stringpattern?@Returns the regular expression !ro'hich this pattern 'as copiled"

String[] split?.harSe)uenceinput@Splits the given input se)uence

around atches o! this pattern"

http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/CharSequence.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/CharSequence.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html

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static boolean matches?Stringregex> .harSe)uenceinput@

.opiles the given regularexpression and attepts to atchthe given input against it"

http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/CharSequence.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/CharSequence.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.html

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Matcher !unctions

boolean fnd?@Attepts to nd the next subse)uence o! theinput se)uence that atches the pattern"

boolean lookingAt?@Attepts to atch the input se)uence>starting at the beginning> against thepattern"

booleanmatches?@Attepts to atch the entire input se)uenceagainst the pattern"

http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.html

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atternpattern?@Returns the pattern that is interpreted b*this atcher"

StringreplaceAll?String replaceent@Replaces ever* subse)uence o! the inputthat atches the pattern 'ith the givenstring"

String replaceFirst?String replaceent@Replaces the rst subse)uence o! the inputthat atches the pattern 'ith the givenstring"

http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.htmlhttp://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Pattern.html

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