多合一 Java 正则表达式、匹配器模式和正则表达式教程

已发表: 2021-09-29
多合一 Java 正则表达式、匹配器模式和正则表达式教程

在本教程中，我们将介绍 Matcher ( java.util.regex.Matcher ) API 的列表。 前一段时间，我写了一篇关于 Java Regex 的教程，其中涵盖了各种各样的示例。

正则表达式是字符串的一种搜索模式。 java.util.regex用于将字符序列与 Java 中正则表达式指定的模式进行匹配的类。

如果您有以下任何问题，本教程最有效：

  • Java 正则表达式 - 教程
  • Java 正则表达式教程
  • Java中的正则表达式是什么？
  • Java中的模式是什么？
  • java模式匹配器示例和java正则表达式特殊字符

让我们开始吧。

  1. 创建类CrunchifyPatternMatcherTutorial.java
  2. 创建不同的方法来检查以下 Matcher API：
    • 火柴（）
    • 看着（）
    • 查找开始结束（）
    • 团体（）
    • 多组（）
    • 全部替换（）
  3. 打印每个 API 的结果。

火柴（）

matches()尝试将整个字符串与模式匹配。 当且only if整个区域序列与此匹配器的模式匹配时，它才返回true 。

看着（）

lookingAt() 功能与matches() 完全相同，只是它尝试匹配输入序列，从区域的开头开始，与模式匹配。 当且仅当输入序列的前缀与此匹配器的模式匹配时，它才返回 true。

查找（），开始（）和结束（）

find()尝试查找与模式匹配的输入序列的下一个子序列。 start()尝试返回前一个匹配的开始索引， end()尝试返回前一个匹配的结束索引。

团体（）

group()返回与前一个匹配项匹配的输入子序列。 这就像 start() 和 end() 之间的匹配。

多组

multiplegroups组可以用“（字符串）（字符串）”表示。

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

全部替换（）

replaceAll()用给定的替换字符串替换与模式匹配的输入序列的每个子序列。

这是一个完整的例子：

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 ) ;
}
 
}

Eclipse 控制台结果：

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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 .

如果您对上述程序有任何疑问，请告诉我。