Greedy quantifiers

Quantifier	Example	Description
?	X?	X, once or not at all
*	X*	X, zero or more times
+	X+	X, one or more times
{n}	X{n}	X, exactly n times
{n,}	X{n,}	X, at least n times
{n,m}	X{n,m}	X, at least n but not more than m times

import java.util.regex.*;
import java.io.*;

public class RegExHarness {
    public static void main(String args[]) throws IOException{
        
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        
        Pattern pattern;
        Matcher matcher;
        
        String regex;
        String text;
              
        while(true){
            try{
                System.out.println("Enter Regular Expression");
                regex = br.readLine();
                pattern = Pattern.compile(regex);

                System.out.println("Enter the string");
                text = br.readLine();
                matcher = pattern.matcher(text);

                matcher.matches();

                System.out.print("I found the text " + matcher.group());
                System.out.print(" starting at index " + matcher.start());
                System.out.println(" Ending at index " + matcher.end());
            }
            catch(Exception e){
                System.out.println(e);
            }
        }     
    }
}

Sample Output

Enter Regular Expression
a?
Enter the string
a
I found the text a starting at index 0 Ending at index 1
Enter Regular Expression
a?
Enter the string
aa
java.lang.IllegalStateException: No match found
Enter Regular Expression
a*
Enter the string
aaaa
I found the text aaaa starting at index 0 Ending at index 4
Enter Regular Expression
a*b
Enter the string
aab
I found the text aab starting at index 0 Ending at index 3
Enter Regular Expression
a+b
Enter the string
aab
I found the text aab starting at index 0 Ending at index 3
Enter Regular Expression
\d{10}
Enter the string
9876543210
I found the text 9876543210 starting at index 0 Ending at index 10
Enter Regular Expression
\d{5,10}
Enter the string
9876
java.lang.IllegalStateException: No match found
Enter Regular Expression
\d{5,10}
Enter the string
987654
I found the text 987654 starting at index 0 Ending at index 6
Enter Regular Expression

Prevoius                                                 Next                                                 Home