greedy quantifier

[Isaac Lee]

I have the following program :

public class Test  
  {  
    public static void main(String[] args)  
    {  
      String str = "f";  
     
      Pattern p = Pattern.compile("f?");  
     
      Matcher m = p.matcher(str);  
      while (m.find())  
      {  
        System.out.println(m.start()+m.group());  
      }  
    }  
  }  

I get the result like this:

0f
1

For the program below:

public class Test  
  {  
    public static void main(String[] args)  
    {  
      String str = "f";  
     
      Pattern p = Pattern.compile("f+");  
     
      Matcher m = p.matcher(str);  
      while (m.find())  
      {  
        System.out.println(m.start()+m.group());  
      }  
    }  
  }  

I get the result :
0f

I don't understand why the results are different. In my understanding, the first program should give the result 0f , the same as the second. why is it different?

Thanks.

[Christophe Verré]

Please check your private messages for an important administrative matter.

[Henry Wong]

In the first case, the pattern is zero or one letter f. In the second case, the pattern is one or more letter f. It is the zero letter f part of the first pattern that allows the second match.

Henry

[Isaac Lee]

Thank you. Henry

[Rahul P Kumar]

[Deleted entire post as "hi-jack." Original in our "deleted" forum. CR]