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PatternSyntaxException class in Java regular expressions

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Release： 2023-09-11 19:37:02

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PatternSyntaxException class in Java regular expressions

PatternSyntaxException Class represents an unchecked exception thrown when a syntax error occurs in a regular expression string. This class contains three main methods, namely -

getDescription() - Returns the description of the error.
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getIndex() - Returns the error index.
getPattern() - Returns the regular expression pattern in which the error occurred.
getMessage() - Returns the complete message containing the error, the index, the regular expression pattern in which the error occurred, and the error in the indicated pattern.

Example

Real-time demonstration

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
public class PatternSyntaxExceptionExample {
   public static void main(String args[]) {
      //Reading String from user
      System.out.println("Enter a String");
      Scanner sc = new Scanner(System.in);String input = sc.nextLine();
      //Regular expression to match first digits of a word
      String regex = "["; //\s+
      //Compiling the regular expression
      try {
         Pattern pattern = Pattern.compile(regex);
         //Retrieving the matcher object
         Matcher matcher = pattern.matcher(input);
         //Replacing all space characters with single space
         String result = matcher.replaceAll(" ");
         System.out.print("Text after removing unwanted spaces: \n"+result);
      }catch(PatternSyntaxException ex){
         System.out.println("Description: "+ex.getDescription());
         System.out.println("Index: "+ex.getIndex());
         System.out.println("Message: "+ex.getMessage());
         System.out.println("Pattern: "+ex.getPattern());
      }
   }
}

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Output

Enter a String
this is a [sample text [
Description: Unclosed character class
Index: 0
Message: Unclosed character class near index 0
[
^
Pattern: [

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