uml classdiagram constructor with parameters

I am a complete ROOKIE at this so I need some help on it.

How would you create uml class diagram and constructors with parameters.

for default (no parameters) you do

policyholder() for diagram and pseudo-code

for parameters would you do the same thing

policyholder (policynumber, service class, and customer age) for class diagrams and pseudo-code.

It also asked to initialize each attribute to value where an object of this type can be instantiated, If a policy number is not between 1000 and 999 inclusive, then set the policy number to 0. (policy number is attribute)

The common way is to write constructors like methods and simply omit the return type.

If you want to be extra clear, you can add <<constructor>> in front.