Match strings with regular expression in ignore case

From the way your question is worded, I'm not entirely sure whether you want the match to be case insensitive or not. This regex:

(?i)[^k][^b].*

uses the flag (?i) to turn off case sensitivity, and should do want you want.

I wouldn't use RegEx for everything.

for(String str : ar)
{
    if(!str.toUpperCase().startsWith("KB"))
        System.out.println(str);
}