Hi sanat kumar,
As far as i know,
"^[a-zA-Z]*$" ---- means an expression starts with a,b,c...z or A,B,C..Z
example, a
Aa
AasdfZadsf
"^[A-Z]\\d[A-Z]\\d[A-Z]\\d$" --- means [A-Z] single char between A,B..Z
\\d means 0,1,...9 any on char
like that "B3E3S1". Note that here not * is given it mean only on char.
to represent
"SLFDJLK3alsdkjf" or
"KHDJKFHJK3" in regular expression use
^[A-Z]
*\\d[a-z]
*$ --- starts with
zore or more capitals, there should be one digits after that zero or more small alphabets.
Hope this helps you.
All The Best