Ce este modelul RegEx (Expresie regulată)? Cum se folosește în Java? Exemplu atasat

Publicat: 2021-01-25
Ce este RegEx Pattern (Expresie regulată)? Cum se folosește în Java?

Ce este RegEx?

Expresia regulată este un model de căutare pentru String. java.util.regex Clase pentru potrivirea secvențelor de caractere cu modelele specificate de expresii regulate în Java.

Puteți folosi Regex pentru:

  • Căutarea textului
  • Extragerea textului
  • Modificarea textului

Să discutăm câteva sintaxe de bază:

Clasele de caractere în Regex:

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.    Dot , any character ( may or may not match line terminators , read on )
\ d    A digit : [ 0 - 9 ]
\ D    A non - digit : [ ^ 0 - 9 ]
\ s    A whitespace character : [ \ t \ n \ x0B \ f \ r ]
\ S    A non - whitespace character : [ ^ \ s ]
\ w    A word character : [ a - zA - Z_0 - 9 ]
\ W    A non - word character : [ ^ \ w ]

Cuantificatori în Regex:

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*       Match 0 or more times
+       Match 1 or more times
?        Match 1 or 0 times
{ n }      Match exactly n times
{ n , }    Match at least n times
{ n , m }    Match at least n but not more than m times

Java Split, de asemenea, un exemplu Regex.

Meta caractere în Regex:

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\    Escape the next meta - character ( it becomes a normal / literal character )
^   Match the beginning of the line
.    Match any character ( except newline )
$    Match the end of the line ( or before newline at the end )
|    Alternation ( ‘ or ’ statement )
( )    Grouping
[ ]    Custom character class

Să începem să lucrăm la exemplu. În exemplul de mai jos vom trece peste 5 exemple de regex diferite.

  1. Cum să analizați rezultatul comenzii de uptime în Java
  2. Verificați dacă adresa URL se termină cu o anumită extensie
  3. Verificați dacă există IP valid
  4. Exemplul ReplaceAll() de regex
  5. Aflați dacă SSN este valid
Java
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package crunchify . com . tutorial ;
 
import java . util . regex . Matcher ;
import java . util . regex . Pattern ;
 
/**
* @author Crunchify.com
*
*/
 
public class CrunchifyRegexTutorial {
 
public static void main ( String [ ] args ) {
crunchifyLoadAndAverageRegex ( ) ;
System . out . println ( "\n==========================\n" ) ;
 
crunchifyFindUrlPattern ( ) ;
System . out . println ( "\n==========================\n" ) ;
 
crunchifyFindIPMatcher ( ) ;
System . out . println ( "\n==========================\n" ) ;
 
crunchifyRegexReplaceAllExample ( ) ;
System . out . println ( "\n==========================\n" ) ;
 
crunchifyValidateSSN ( ) ;
}
 
// Find if SSN is valid
private static void crunchifyValidateSSN ( ) {
String ssn1 = "123-45-6789" ;
String ssn2 = "123-456-789" ;
String pattern = "^(\\d{3}-?\\d{2}-?\\d{4})$" ;
 
if ( ssn1 . matches ( pattern ) ) {
System . out . println ( "SSN " + ssn1 + " is valid" ) ;
} else {
System . out . println ( "SSN " + ssn1 + " is NOT valid" ) ;
}
 
if ( ssn2 . matches ( pattern ) ) {
System . out . println ( "SSN " + ssn2 + " is valid" ) ;
} else {
System . out . println ( "SSN " + ssn2 + " is NOT valid" ) ;
}
 
}
 
// ReplaceAll() Example
private static void crunchifyRegexReplaceAllExample ( ) {
String find = "Java" ;
String line = "This is Crunchify.com Java Tutorial." ;
String replace = "Spring MVC" ;
 
Pattern p = Pattern . compile ( find ) ;
Matcher m = p . matcher ( line ) ;
 
// This line will find "Java" and replace it with "Spring MVC"
line = m . replaceAll ( replace ) ;
System . out . println ( line ) ;
 
}
 
// Check if valid IP present
private static void crunchifyFindIPMatcher ( ) {
Pattern validIPPattern = Pattern . compile ( "^(?:[0-9]{1,3}\\.){3}[0-9]{1,3}$" ) ;
System . out . println ( "192.abc.0.1 : " + validIPPattern . matcher ( "192.abc.0.1" ) . find ( ) ) ;
System . out . println ( "192.168.0.1 : " + validIPPattern . matcher ( "192.168.0.1" ) . find ( ) ) ;
}
 
// Check if URL ends with specific extension
private static void crunchifyFindUrlPattern ( ) {
String pattern = ".*\\.(ico|jpg|png|gif|tif|bmp|JPG|PNG|GIF|TIF|BMP)" ;
Pattern r = Pattern . compile ( pattern ) ;
 
Matcher m = r . matcher ( "https://crunchify.com/favicon.ico" ) ;
if ( m . find ( ) ) {
System . out . println ( "URL pattern found" ) ;
} else {
System . out . println ( "URL pattern doesn't found" ) ;
}
 
}
 
// How to Parse "uptime" command result in Java
public static void crunchifyLoadAndAverageRegex ( ) {
Pattern uptimePattern = Pattern . compile ( "^.*\\s+load\\s+average:\\s+([\\d\\.]+),\\s+([\\d\\.]+),\\s+([\\d\\.]+)$" ) ;
 
String output = " 10:17:32 up 189 days, 18:49,  5 user,  load average: 2.07, 1.11, 1.16" ;
Matcher m = uptimePattern . matcher ( output ) ;
 
if ( m . matches ( ) ) {
final double crunchify1MinuteLoadAvg = Double . parseDouble ( m . group ( 1 ) ) ;
final double crunchify5eMinuteloadAvg = Double . parseDouble ( m . group ( 2 ) ) ;
final double crunchify15MinuteLoadAvg = Double . parseDouble ( m . group ( 3 ) ) ;
 
System . out . println ( "Load Average 1 min: " + crunchify1MinuteLoadAvg ) ;
System . out . println ( "Load Average 5 min: " + crunchify5eMinuteloadAvg ) ;
System . out . println ( "Load Average 15 min: " + crunchify15MinuteLoadAvg ) ;
} else {
System . out . println ( "no matches found" ) ;
}
 
}
}

Ieșire:

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Load Average 1 min : 2.07
Load Average 5 min : 1.11
Load Average 15 min : 1.16
 
==========================
 
URL pattern found
 
==========================
 
192.abc.0.1 : false
192.168.0.1 : true
 
==========================
 
This is Crunchify . com Spring MVC Tutorial .
 
==========================
 
SSN 123 - 45 - 6789 is valid
SSN 123 - 456 - 789 is NOT valid

Cum se validează puterea parolei folosind codul Java?

Găsiți mai jos condițiile mele:

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#   must contains one digit from 0-9
( ? = . * [ a - z ] ) must contains one lowercase characters
( ? = . * [ A - Z ] ) must contains one uppercase characters
( ? = . * [ ! @ #$%]) must contains one special symbols in the list "!@#$%"
. match anything with previous condition checking
{ 8 , 25 } length at least 8 characters and maximum of 25

CrunchifyPasswordVerification.java

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package crunchify . com . tutorial ;
 
import java . util . ArrayList ;
import java . util . List ;
import java . util . regex . Matcher ;
import java . util . regex . Pattern ;
 
/**
* @author Crunchify.com
*
*/
public class CrunchifyPasswordVerification {
public static void main ( String [ ] args ) {
 
String pattern = "((?=.*[@!#$%])(?=.*[a-z])(?=.*[A-Z])(?=.*\\d).{8,22})" ;
Pattern r = Pattern . compile ( pattern ) ;
 
List <String> input = new ArrayList <String> ( ) ;
input . add ( "Crunchify" ) ;
input . add ( "Crunchify123#" ) ;
input . add ( "crunchify123#" ) ;
input . add ( "crunchify** " ) ;
input . add ( "Crunchify123!!" ) ;
 
for ( String password : input ) {
Matcher m = r . matcher ( password ) ;
if ( m . matches ( ) )
System . out . println ( "Password: " + password + " is valid" ) ;
else
System . out . println ( "Password: " + password + " is NOT valid" ) ;
}
 
}
}

Rezultat:

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Password: Crunchify is NOT valid
Password: Crunchify123# is valid
Password: crunchify123# is NOT valid
Password: crunchify**  is NOT valid
Password: Crunchify123!! is valid