Delete one part of the String

I have this String :

String myStr = "something.bad@foo.us"

I want to get just the "something.bad" from myStr ?

You just need to use substring having found the right index to chop at:

int index = myStr.indexOf('@');
// TODO: work out what to do if index == -1

String firstPart = myStr.substring(0, index);

EDIT: Fairly obviously, the above takes the substring before the first @. If you want the substring before the last @ you would write:

int index = myStr.lastIndexOf('@');
// TODO: work out what to do if index == -1

String firstPart = myStr.substring(0, index);

You can use

String str = myStr.split("@")[0];

It will split the string in two parts and then you can get the first String element