How to replace first occarnce of "." in a String?

Hi,
I used the replaceFirst() to solve the problem but replaceFirst() method behaviour is very strange when we are dealing with ".".

The scenarios i executed are as follows:

1)This scenario worked as expected.
Input :"Hello.world.app".replace(".", "@");
Output : Hello@world@app

2)Giving wild behaviour.
Input :"Hello.world.app".replaceFirst(".", "@")
Output : @ello.world.app

3)Giving wild behaviour.
Input :"Hello.world.app".replaceAll(".", "@")
Output : @@@@@@@@@@@@@@@

4)This scenario worked as expected.
Input :"Hello.world.app".replaceAll("p", "@")
Output : Hello.world.a@@

5)This scenario worked as expected.
Input :"Hello.world.app".replaceFirst("p", "@")
Output : Hello.world.a@p

Can any one tell me why the replaceFirst(), replaceAll() methods failed to replace the "." ?

Thanks,
Kumar.

Originally posted by Kumara Swamy D:
Hi,
I used the replaceFirst() to solve the problem but replaceFirst() method behaviour is very strange when we are dealing with ".".

The scenarios i executed are as follows:

2)Giving wild behaviour.
Input :"Hello.world.app".replaceFirst(".", "@")
Output : @ello.world.app

Can you look at the Java docs for the above methods, its clearly mention that first parameter is taken as Regular Expression. If you are good with Regular expression, you don't face this problem OR Study Regular Expression in Java

Hi Sagar Rohankar,

Thanks for your quick and perfect reply.
The url helped me a lot to know about "regex".
The issue is resolved.

Thanks once again

Thanks,
Kumar.

You are welcome..

Sagar Rohankar, well done. A good example of how to help somebody to learn

Originally posted by Campbell Ritchie:
Sagar Rohankar, well done. A good example of how to help somebody to learn

that's because, I learnt lots from your post and fellow Ranchers. Really a good site for beginners like me .. I highly appreciate the efforts taken by all Ranchers..

Aw shucks . . . you've got me all embarrassed now.

You're welcome