Java Regex - PatternSyntaxException Class

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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

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.

Live Demo 
package com.howcodex;

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: [
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