import java.util.Scanner;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class RegexTester {

    public static void main(String[] args){
        RegexTester rt=new RegexTester();
        while(true) {
            rt.checkRegularExpression();
        }
    }
    public void checkRegularExpression() {       
        Scanner sc=new Scanner(System.in);
        System.out.print("Enter Regular expression pattern : ");
        String regex=sc.nextLine();
        while(check(regex));
    }
    public boolean check(String regex) {
        Scanner sc=new Scanner(System.in);
        System.out.print("Enter data: ");
        String data=sc.nextLine();
            Pattern samplePattern = Pattern.compile(regex);
            Matcher matcher = samplePattern.matcher(data);
            boolean found = false;
            while (matcher.find()) {
                System.out.format("Text \"%s\" is found : from index %d - to index %d.\n",
                    matcher.group(), matcher.start(), matcher.end());
                found = true;
            }
            if(!found){
                System.out.format("No match found.\n");
            }
            System.out.print("Check another data ? [Y or y] or Quit [Q or q] : ");
            String another=sc.nextLine();
            if(another.equals("Q") || another.equals("q")) {
                System.exit(0);
                return false;
            } else if(another.equals("Y") || another.equals("y")) {
                return true;
            } else {
                return false;
            }
    }

}

Enter Regular expression pattern : [abc]
Enter data: abcdefg
Text "a" is found : from index 0 - to index 1.
Text "b" is found : from index 1 - to index 2.
Text "c" is found : from index 2 - to index 3.
Check another data ? [Y or y] or Quit [Q or q] : y
Enter data:
No match found.
Check another data ? [Y or y] or Quit [Q or q] : y
Enter data: cbfhgft
Text "c" is found : from index 0 - to index 1.
Text "b" is found : from index 1 - to index 2.
Check another data ? [Y or y] or Quit [Q or q] : q