1. Match Exactly 3 Occurrences Using {n}
This program demonstrates the {n} quantifier in Java regular expressions. The {n} matches exactly n occurrences of the preceding character or group. Here, {3} matches exactly three consecutive occurrences of the character a.
import java.util.regex.*;
public class ExactOccurrences {
public static void main(String[] args) {
String input = "aaa aaaa aa";
Pattern pattern = Pattern.compile("a{3}");
Matcher matcher = pattern.matcher(input);
while (matcher.find()) {
System.out.println("Matched: " + matcher.group());
}
}
}Output:
Matched: aaa
Matched: aaa2. Match Exactly 2 Digits Using {n}
This program uses {2} to match exactly two consecutive digits. The pattern matches only groups containing two digits at a time. It does not match a single digit by itself.
import java.util.regex.*;
public class ExactDigitOccurrences {
public static void main(String[] args) {
String input = "12 123 4567";
Pattern pattern = Pattern.compile("\\d{2}");
Matcher matcher = pattern.matcher(input);
while (matcher.find()) {
System.out.println("Matched: " + matcher.group());
}
}
}Output:
Matched: 12
Matched: 12
Matched: 45
Matched: 67