The PatternSyntaxException class represents an unchecked exception thrown in case of a syntax error in regex string. This class contains three main methods namely −
getDescription() − Returns the description of the error.
getIndex() − Returns the error index.
getPattern() − Returns the regular expression pattern with error.
getMessage() − Returns the complete message congaing the error, index, regular expression pattern with error, indication of the error in the pattern.
Example
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());
}
}
}Output
Enter a String this is a [sample text [ Description: Unclosed character class Index: 0 Message: Unclosed character class near index 0 [ ^ Pattern: [