Reluctant quantifiers Java Regular expressions


Greedy quantifiers are the default quantifiers. A greedy quantifier matches as much as possible from the input string (longest match possible) if match not occurred it leaves the last character and matches again.

Whereas a reluctant or, non-greedy quantifier matches as little as possible, initially the non-greedy quantifier matches the first character if match not occurred it adds another character from the input string and tries to match.

If you place a "?" after a greedy quantifier it becomes reluctant or non-greedy quantifier. Following is the list of reluctant quantifiers −

QuantifierDescription
re*?Matches zero or more occurrences.
re??Matches zero or, 1 occurrence.
re+?Matches one or more occurrences.
re{n}?Matches exactly n occurrences.
re{n, }?Matches at least n occurrences.
re{n, m}?Matches at least n and at most m occurrences.

Example

 Live Demo

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Test {
   public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);
      System.out.println("Enter input text: ");
      String input = sc.nextLine();
      String regex = "[0-9]+?";
      //Creating a pattern object
      Pattern pattern = Pattern.compile(regex);
      //Matching the compiled pattern in the String
      Matcher matcher = pattern.matcher(input);
      while (matcher.find()) {
         System.out.print("Pattern found from " + matcher.start()+ " to " + (matcher.end()-1)+"::");
         System.out.print(matcher.group());
         System.out.println();
      }
   }
}

Output

Enter input text:
12345678
Pattern found from 0 to 0::1
Pattern found from 1 to 1::2
Pattern found from 2 to 2::3
Pattern found from 3 to 3::4
Pattern found from 4 to 4::5
Pattern found from 5 to 5::6
Pattern found from 6 to 6::7
Pattern found from 7 to 7::8
raja
Published on 13-Jan-2020 05:52:12
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