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 −
| Quantifier | Description |
|---|---|
| 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
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