pattern matching

[vineet walia]

import java.util.regex.*;
public class search_02 {
public static void main(String str [])
{
	Pattern p=Pattern.compile("a*"); // regx
	Matcher m=p.matcher("oblaada oblaadi");// target string
	while(m.find())
		System.out.println(" "+m.start());
	
}
}

its output is:
0
1
2
3
5
6
7
8
9
10
11
13
14
15

2nd code is:

import java.util.regex.*;
public class search_02 {
public static void main(String str [])
{
	Pattern p=Pattern.compile("aa*"); // regx
	Matcher m=p.matcher("oblaada oblaadi");// target string
	while(m.find())
		System.out.println(" "+m.start());
	
}
}

its output is:
3
6
11
* will match 0 or more times
please explain difference in output

[Rajeev Rnair]

First one is using "a*" which means 0 or more occurences of a. So it checks each and every character from 0 to length().
Second one is "aa*, which means "a" and THEN "a*". First there has to be "a" and then 0 or more occurences of "a". There are only 3 cases like that, hense the output is like that!

Hope this helps!

[vineet walia]

thank you so much brother

[vineet walia]

one more thing in first case
"oblaada oblaadi"
15 character

so why its is starting at 0 and end at 15(it should be at 14)?

[Rajeev Rnair]

vineet walia wrote:one more thing in first case
"oblaada oblaadi"
15 character

so why its is starting at 0 and end at 15(it should be at 14)?

You are welcome mate!
This is a special case with the '*' meta character, and it always look after the last character! Please go through the K&B book chapter for Patterns and Regex.

Wish you all the best!