Explain quantifiers in Java regular expressions

JavaObject Oriented ProgrammingProgramming

If you want to specify the number of occurrences while constructing a regular expression you can use quantifiers. Following table lists out the quantifiers supported by Java regular expressions −

QuantifierDescriptionExample
re*zero or more occurrences.
[0-9]*: matches 0 or more digits.
re?One or, no occurrences at all.
[0-9]?: matches 0 or 1 digit.
re+one or more occurrences.
[0-9]+: matches one or more digits.
re{n}n occurrences.
[0-9]{3}: matches 3 digits.
re{n, }at-least n occurrences.
[0-9]{3, }: matches at least 3 digits.
re{n, m}at-least n and at-most m occurrences.
[0-9]{2, 5}: matches if given input is a number with 3 to 5 digits.

Example

 Live Demo

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Example {
   public static void main( String args[] ) {
      String regex = "[0-9]{3,6}";
      Scanner sc = new Scanner(System.in);
      System.out.println("Enter 5 input strings: ");
      String input[] = new String[5];
      for (int i=0; i<5; i++) {
         input[i] = sc.nextLine();
      }
      //Creating a Pattern object
      Pattern p = Pattern.compile(regex);
      System.out.println("Matched values: ");
      for(int i=0; i<5;i++) {
         //Creating a Matcher object
         Matcher m = p.matcher(input[i]);
         if(m.matches()) {
            System.out.println(m.group()+": accepted ");
         }
      }
   }
}

Output

Enter 5 input strings:
12
154
4587
478365
4578952
Matched values:
154: accepted
4587: accepted
478365: accepted
raja
Published on 10-Jan-2020 17:25:24
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