Tutorial Java Regex, Matcher Pattern ed espressioni regolari tutto in uno

Pubblicato: 2021-09-29
Tutorial Java Regex, Matcher Pattern ed espressioni regolari tutto in uno

In questo tutorial esamineremo l'elenco delle API Matcher ( java.util.regex.Matcher ). Qualche tempo fa ho scritto un tutorial su Java Regex che copre un'ampia varietà di campioni.

Regular Expression è un modello di ricerca per String. java.util.regex Classi per la corrispondenza di sequenze di caratteri con modelli specificati da espressioni regolari in Java.

Questo tutorial funziona meglio se hai una delle seguenti domande:

  • Regex Java – Tutorial
  • Esercitazioni sulle espressioni regolari Java
  • Che cos'è l'espressione regolare in Java?
  • Che cos'è il modello in Java?
  • esempio di java pattern matcher e caratteri speciali java regex

Iniziamo.

  1. Crea classe CrunchifyPatternMatcherTutorial.java
  2. Crea diversi metodi per controllare sotto le API Matcher:
    • corrisponde ()
    • guardando()
    • trovaInizioFine()
    • gruppo()
    • piùGruppi()
    • sostituisci tutto()
  3. Stampa il risultato di ciascuna API.

corrisponde ()

matches() cerca di abbinare l'intera stringa al modello. Restituisce true se, e only if , l'intera sequenza della regione corrisponde al modello di questo abbinamento.

guardando()

La funzionalità lookingAt() è esattamente la stessa di match() tranne per il fatto che cerca di far corrispondere la sequenza di input, a partire dall'inizio della regione, rispetto al modello. Restituisce true se, e solo se, un prefisso della sequenza di input corrisponde al modello di questo abbinamento.

trova(), inizio() e fine()

find() tenta di trovare la successiva sottosequenza della sequenza di input che corrisponde al modello. start() tenta di restituire l'indice di inizio della corrispondenza precedente e end() tenta di restituire l'indice di fine della corrispondenza precedente.

gruppo()

group() restituisce la sottosequenza di input corrispondente alla corrispondenza precedente. È come una corrispondenza tra start() e end().

piùGruppi

multiplegroups possono essere rappresentati da "(String) (String)".

Esempio: String crunchifyPattern = "(is) (.+?) (.+?) " ;

sostituisci tutto()

replaceAll() sostituisce ogni sottosequenza della sequenza di input che corrisponde al modello con la stringa di sostituzione data.

Ecco un esempio completo:

Java
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package crunchify . com . tutorials ;
 
import java . util . regex . Matcher ;
import java . util . regex . Pattern ;
 
/**
* @author Crunchify.com
* All in one Java Regex, Matcher Pattern and Regular Expressions Tutorial.
*/
 
public class CrunchifyPatternMatcherTutorial {
 
public static void main ( String [ ] args ) {
String crunchifyData = "This is Java Regex Pattern Example. https://crunchify.com. This is the list of all Matcher Example" ;
System . out . println ( "This is sample data 'crunchifyData': " + crunchifyData ) ;
crunchifyMatches ( crunchifyData ) ;
crunchifyLookingAt ( crunchifyData ) ;
crunchifyFindStartEnd ( crunchifyData ) ;
 
String crunchifyData2 = "Crunchify is a Web company. Google is a Search company. Facebook is a social company." ;
crunchifyGroup ( crunchifyData2 ) ;
crunchifyMultipleGroups ( crunchifyData2 ) ;
crunchifyReplaceAll ( crunchifyData2 ) ;
}
 
// crunchifyMatcher.replaceAll()
private static void crunchifyReplaceAll ( String crunchifyData2 ) {
String crunchifyPattern = "company" ;
// Pattern: A compiled representation of a regular expression.
// A regular expression, specified as a string, must first be compiled into an instance of this class.
// The resulting pattern can then be used to create a Matcher object that can match arbitrary character sequences against the regular expression.
// All of the state involved in performing a match resides in the matcher, so many matchers can share the same pattern.
// compile(): Compiles the given regular expression into a pattern.
Pattern pat = Pattern . compile ( crunchifyPattern ) ;
// matcher(): Creates a matcher that will match the given input against this pattern.
Matcher crunchifyMatcher = pat . matcher ( crunchifyData2 ) ;
// replaceAll(): Replaces every subsequence of the input sequence that matches the pattern with the given replacement string.
// This method first resets this matcher. It then scans the input sequence looking for matches of the pattern. Characters that are not part of any match are appended directly to the result string; each match is replaced in the result by the replacement string.
// The replacement string may contain references to captured subsequences as in the appendReplacement method.
String updatedString = crunchifyMatcher . replaceAll ( "best company" ) ;
System . out . println ( "replaceAll() - updated String: " + updatedString ) ;
}
 
private static void crunchifyMultipleGroups ( String crunchifyData2 ) {
String crunchifyPattern = "(is) (.+?) (.+?) " ;
Pattern pat = Pattern . compile ( crunchifyPattern ) ;
Matcher crunchifyMatcher = pat . matcher ( crunchifyData2 ) ;
// find(): Attempts to find the next subsequence of the input sequence that matches the pattern.
while ( crunchifyMatcher . find ( ) ) {
// group(): Returns the input subsequence matched by the previous match.
// For a matcher m with input sequence s, the expressions m.group() and s.substring(m.start(), m. end()) are equivalent.
// Note that some patterns, for example a*, match the empty string.
// This method will return the empty string when the pattern successfully matches the empty string in the input.
System . out . println ( "multipleGroup() result: " + crunchifyMatcher . group ( ) ) ;
}
}
 
// crunchifyMatcher.group()
private static void crunchifyGroup ( String crunchifyData2 ) {
String crunchifyPattern = "company" ;
Pattern pat = Pattern . compile ( crunchifyPattern ) ;
Matcher crunchifyMatcher = pat . matcher ( crunchifyData2 ) ;
while ( crunchifyMatcher . find ( ) ) {
System . out . println ( "group() result: " + crunchifyMatcher . group ( ) ) ;
}
}
 
// crunchifyMatcher.find() - start() - end()
private static void crunchifyFindStartEnd ( String crunchifyData ) {
String crunchifyPattern = "Example" ;
Pattern pat = Pattern . compile ( crunchifyPattern ) ;
Matcher crunchifyMatcher = pat . matcher ( crunchifyData ) ;
int totalCount = 0 ;
while ( crunchifyMatcher . find ( ) ) {
totalCount ++ ;
// start(): Returns the start index of the previous match.
// end(): Returns the offset after the last character matched.
System . out . println ( "findStartEnd result = Iteration " + totalCount + " : " + crunchifyMatcher . start ( ) + " - "
+ crunchifyMatcher . end ( ) ) ;
}
}
 
// crunchifyMatcher.lookingAt()
private static void crunchifyLookingAt ( String crunchifyData ) {
String crunchifyPattern = "This is Java" ;
Pattern pat = Pattern . compile ( crunchifyPattern ) ;
Matcher crunchifyMatcher = pat . matcher ( crunchifyData ) ;
// lookingAt(): Attempts to match the input sequence, starting at the beginning of the region, against the pattern.
boolean isLookingAt = crunchifyMatcher . lookingAt ( ) ;
System . out . println ( "lookingAt() result 1: " + isLookingAt ) ;
 
crunchifyPattern = " is Java" ;
pat = Pattern . compile ( crunchifyPattern ) ;
crunchifyMatcher = pat . matcher ( crunchifyData ) ;
isLookingAt = crunchifyMatcher . lookingAt ( ) ;
System . out . println ( "lookingAt() result 2: " + isLookingAt ) ;
 
}
 
// crunchifyMatcher.matches()
public static void crunchifyMatches ( String crunchifyData ) {
String crunchifyPattern = ".*https://.*" ;
 
Pattern pat = Pattern . compile ( crunchifyPattern ) ;
Matcher crunchifyMatcher = pat . matcher ( crunchifyData ) ;
boolean isMatched = crunchifyMatcher . matches ( ) ;
System . out . println ( "matches() result: " + isMatched ) ;
}
 
}

Risultato console Eclipse:

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This is sample data 'crunchifyData' : This is Java Regex Pattern Example . https : //crunchify.com. This is the list of all Matcher Example
matches ( ) result : true
lookingAt ( ) result 1 : true
lookingAt ( ) result 2 : false
findStartEnd result = Iteration 1 : 27 - 34
findStartEnd result = Iteration 2 : 90 - 97
group ( ) result : company
group ( ) result : company
group ( ) result : company
multipleGroup ( ) result : is a Web
multipleGroup ( ) result : is a Search
multipleGroup ( ) result : is a social
replaceAll ( ) - updated String : Crunchify is a Web best company . Google is a Search best company . Facebook is a social best company .

Fammi sapere se hai qualche domanda in esecuzione sopra il programma.