Regular Expression "re*" Metacharacter in Java

The subexpression/metacharacter “re*” matches 0 or more occurrences of the preceding expression.

Example 1

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexExample {
   public static void main( String args[] ) {
      String regex = "aabc*";
      String input = "aabcabcaabcabbcaabcbcaabc";
      Pattern p = Pattern.compile(regex);
      Matcher m = p.matcher(input);
      int count = 0;
      while(m.find()) {
         count++;
      }
      System.out.println("Number of matches: "+count);
   }
}

Output

Number of matches: 4

Example 2

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MatchAllCharacters {
   public static void main( String args[] ) {
      String regex = "(.*)?(\d+)";
      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("Strings containing digits: ");
      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());
         }
      }
   }
}

Output

test data
hello how are you 335
welcome to Tutorialspoint
Strings containing digits:
sample text 1
hello how are you 335