Bank transaction system
A number of points:


Do not use floating-point data types (float or double) for amounts of money. Floating-point data types have limited precision, they cannot represent all decimal values exactly, and you're going to get roundoff errors sooner or later. Use integers instead (int or long) and store cents instead (for example, 1040 cents) or use BigDecimal.
Make member variables private by default; only make them protected (or another access level) if there is a good reason to do so.
Prefer local variables above member variables. Is there a good reason why s is a member variable instead of a local variable?
Don't write the main part of a program in the constructor of a class. You have the main part of your program in the constructor of the Bank class. The constructor is meant to initialize the state of a new object, so the only thing that the constructor should do is initialize member variables.
In your constructor, you catch an InputMismatchException and print an error message ("bye bye...") but you are not actually returning from the constructor. So execution will continue and print "Incorrect PIN entered ..." which is not what you meant.
The program doesn't actually do what you'd expect it to do; withdrawal, deposit etc. functionality never gets called anywhere.
You need a public static void main(String[] args) method to be able to run this as a stand-alone program.