Author: saqibkhan

A greedy quantifier indicates to search engine to search the entire string and check whether it matches the given regexp. Following are various examples of Greedy Quantifiers using regular expression in java.

Sr.No	Construct & Matches
1	X?X, once or not at all.
2	X*X, zero or more times
3	X+X, one or more times.
4	X{n}X, exactly n times.
5	X{n,}X, at least n times.
6	X{n,m}X, at least n but not more than m times

Following are various examples of Boundary Matchers using regular expression in java.

Sr.No	Construct & Matches
1	^The beginning of a line.
2	$The end of a line.
3	\bA word boundary.
4	\BA non-word boundary.
5	\AThe beginning of the input.
6	\GThe end of the previous match.
7	\ZThe end of the input but for the final terminator, if any.
8	\zThe end of the input.

Following are various examples of matching Unicode character classes using regular expression in java.

Sr.No	Construct & Matches
1	\p{IsLatin}A Latin script character.
2	\p{InGreek}A character in the Greek block.
3	\p{Lu}An uppercase letter.
4	\p{IsAlphabetic}An alphabetic character (binary property).
5	\p{Sc}A currency symbol.
6	\P{InGreek}Any character except one in the Greek block.
7	[\p{L}&&[^\p{Lu}]]Any letter except an uppercase letter.

Following are various examples of matching JAVA character classes using regular expression in java.

Sr.No	Construct & Matches
1	\p{javaLowerCase}Equivalent to java.lang.Character.isLowerCase().
2	\p{javaUpperCase}Equivalent to java.lang.Character.isUpperCase().
3	\p{javaWhitespace}Equivalent to java.lang.Character.isWhitespace().
4	\p{javaMirrored}Equivalent to java.lang.Character.isMirrored().

Following are various examples of matching POSIX character classes using regular expression in java.

Sr.No	Construct & Matches
1	\p{Lower}A lower-case alphabetic character: [a-z].
2	\p{Upper}An upper-case alphabetic character:[A-Z].
3	\p{ASCII}All ASCII:[\x00-\x7F].
4	\p{Alpha}An alphabetic character:[\p{Lower}\p{Upper}].
5	\p{Digit}A decimal digit: [0-9].
6	\p{Alnum}An alphanumeric character:[\p{Alpha}\p{Digit}].
7	\p{Punct}Punctuation: One of !”#$%&'()*+,-./:;<=>?@[\]^_>{|}<.
8	\p{Graph}A visible character: [\p{Alnum}\p{Punct}].
9	\p{Print}A printable character: [\p{Graph}\x20].
10	\p{Blank}A space or a tab: [ \t].
11	\p{XDigit}A hexadecimal digit: [0-9a-fA-F].
12	\p{Space}A whitespace character: [ \t\n\x0B\f\r].

Following are various examples of matching predefined character classes using regular expression in java.

Sr.No	Construct & Matches
1	.Any character (may or may not match line terminators).
2	\dA digit: [0-9].
3	\DA non-digit: [^0-9].
4	\sA whitespace character: [ \t\n\x0B\f\r]
5	\SA non-whitespace character: [^\s].
6	\wA word character: [a-zA-Z_0-9].
7	\WA non-word character: [^\w]

Following are various examples of matching character classes using regular expression in java.

Sr.No	Construct & Matches
1	[abc]a, b, or c (simple class).
2	[^abc]Any character except a, b, or c (negation).
3	[a-zA-Z]a through z or A through Z, inclusive (range).
4	[a-d[m-p]]a through d, or m through p: [a-dm-p] (union).
5	[a-z&&[def]]d, e, or f (intersection).
6	[a-z&&[^bc]]a through z, except for b and c: [ad-z] (subtraction)
7	[a-z&&[^m-p]]a through z, and not m through p: [a-lq-z](subtraction).

Following are various examples of matching characters using regular expression in java.

Sr.No	Construct & Matches
1	xThe character x
2	\\The backslash character
3	\0nThe character with octal value 0n (0 ≤ n ≤ 7)
4	\0nnThe character with octal value 0nn (0 ≤ n ≤ 7)
5	\0mnnThe character with octal value 0mnn (0 ≤ m ≤ 3, 0 ≤ n ≤ 7)
6	\xhhThe character with hexadecimal value 0xhh
7	\uhhhhThe character with hexadecimal value 0xhhhh
8	\tThe tab character (‘\u0009’)
9	\nThe newline (line feed) character (‘\u000A’)
10	\rThe carriage-return character (‘\u000D’)
11	\fThe form-feed character (‘\u000C’)

Introduction

The java.util.regex.PatternSyntaxException class represents a unchecked exception thrown to indicate a syntax error in a regular-expression pattern.

Class declaration

Following is the declaration for java.util.regex.PatternSyntaxException class −

public class PatternSyntaxException
   extends IllegalArgumentException

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Constructors

Sr.No	Method & Description
1	PatternSyntaxException(String desc, String regex, int index)Constructs a new instance of this class.

Class methods

Sr.No	Method & Description
1	String getDescription()Retrieves the description of the error.
2	int getIndex()Retrieves the error index.
3	String getMessage()Returns a multi-line string containing the description of the syntax error and its index, the erroneous regular-expression pattern, and a visual indication of the error index within the pattern.
4	String getPattern()Retrieves the erroneous regular-expression pattern.

Methods inherited

This class inherits methods from the following classes −

• Java.lang.Throwable
• Java.lang.Object

Example

The following example shows the usage of java.util.regex.Pattern.PatternSyntaxException class methods.

package com.tutorialspoint;

import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

public class PatternSyntaxExceptionDemo {
   private static String REGEX = "[";
   private static String INPUT = "The dog says meow " + "All dogs say meow.";
   private static String REPLACE = "cat";

   public static void main(String[] args) {
  try{
     Pattern pattern = Pattern.compile(REGEX);
     
     // get a matcher object
     Matcher matcher = pattern.matcher(INPUT); 
     INPUT = matcher.replaceAll(REPLACE);
  } catch(PatternSyntaxException e){
     System.out.println("PatternSyntaxException: ");
     System.out.println("Description: "+ e.getDescription());
     System.out.println("Index: "+ e.getIndex());
     System.out.println("Message: "+ e.getMessage());
     System.out.println("Pattern: "+ e.getPattern());
  }
   }
}

Let us compile and run the above program, this will produce the following result −

PatternSyntaxException: 
Description: Unclosed character class
Index: 0
Message: Unclosed character class near index 0
[
^
Pattern: [

Introduction

The java.util.regex.Matcher class acts as an engine that performs match operations on a character sequence by interpreting a Pattern.

Class declaration

Following is the declaration for java.util.regex.Matcher class −

public final class Matcher
   extends Object
  implements MatchResult

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Class methods

Sr.No	Method & Description
1	Matcher appendReplacement(StringBuffer sb, String replacement)Implements a non-terminal append-and-replace step.
2	StringBuffer appendTail(StringBuffer sb)Implements a terminal append-and-replace step.
3	int end()Returns the offset after the last character matched.
4	int end(int group)Returns the offset after the last character of the subsequence captured by the given group during the previous match operation.
5	boolean find()Attempts to find the next subsequence of the input sequence that matches the pattern.
6	boolean find(int start)Resets this matcher and then attempts to find the next subsequence of the input sequence that matches the pattern, starting at the specified index.
7	String group()Returns the input subsequence captured by the given group during the previous match operation.
8	String group(String name)Returns the input subsequence captured by the given named-capturing group during the previous match operation.
9	int groupCount()Returns the number of capturing groups in this matcher’s pattern.
10	boolean hasAnchoringBounds()Queries the anchoring of region bounds for this matcher.
11	boolean hasTransparentBounds()Queries the transparency of region bounds for this matcher.
12	boolean hitEnd()Returns true if the end of input was hit by the search engine in the last match operation performed by this matcher.
13	boolean lookingAt()Attempts to match the input sequence, starting at the beginning of the region, against the pattern.
14	boolean matches()Attempts to match the entire region against the pattern.
15	Pattern pattern()Returns the pattern that is interpreted by this matcher.
16	static String quoteReplacement(String s)Returns a literal replacement String for the specified String.
17	Matcher region(int start, int end)Sets the limits of this matcher’s region.
18	int regionEnd()Reports the end index (exclusive) of this matcher’s region.
19	int regionStart()Reports the start index of this matcher’s region.
20	String replaceAll(String replacement)Replaces every subsequence of the input sequence that matches the pattern with the given replacement string.
21	String replaceFirst(String replacement)Replaces the first subsequence of the input sequence that matches the pattern with the given replacement string.
22	boolean requireEnd()Returns true if more input could change a positive match into a negative one.
23	Matcher reset()Resets this matcher.
24	Matcher reset(CharSequence input)Resets this matcher with a new input sequence.
25	int start()Returns the start index of the previous match.
26	int start(int group)Returns the start index of the subsequence captured by the given group during the previous match operation.
27	MatchResult toMatchResult()Returns the match state of this matcher as a MatchResult.
28	String toString()Returns the string representation of this matcher.
29	Matcher useAnchoringBounds(boolean b)Sets the anchoring of region bounds for this matcher.
30	Matcher usePattern(Pattern newPattern)Changes the Pattern that this Matcher uses to find matches with.
31	Matcher useTransparentBounds(boolean b)Sets the transparency of region bounds for this matcher.

Methods inherited

This class inherits methods from the following classes −

• Java.lang.Object