Question

class Parking Permit has seven fields, but only of three of them are required for issuing a parking permit. Implement ways to instantiate this class with three required fields and arbitrary number of optional optional fields. You cannot use setter methods. class ParkingPermit{ String make; String model; String Licenceplate; String year; //Optional String VIN; //Optional Strig color; // Optional String Owner; // Optional }

Answer 1

To instantiate any class, we need to ahve constructors. As the question asked, there are 3 mandatory fileds and 4 optional fields for ParkingPermit. and we can not use setters and getters. So the only way we can give values to these fileds is by constructors. So we will instatiate this class by using overloaded constructors. We will have diffrent constructors with diffrent fields. All constructors have three mandatory fileds plus the optional fields. we can use any one of them to instantiate the class and set the values in required fields. Any field that is not given value through constructor parametrs will be set "Not Defined". I have provided 4 constructors or in other words 4 diffrent ways to instantiate the class. below is the class code with all 4 constructors.

public class ParkingPermit {
        String make;
        String model;
        String LicencePlate;
        String year;
        String VIN;
        String color;
        String Owner;
        
        //Constructor with all parameters
        //instantiate by giving all the parameters
        public ParkingPermit(String make, String model, String licencePlate, String year, String vIN, String color,
                        String owner) {
                this.make = make;
                this.model = model;
                LicencePlate = licencePlate;
                this.year = year;
                VIN = vIN;
                this.color = color;
                Owner = owner;
        }

        //constructor with 4 parametrs, 3 mandatory and 1 optional
        //instantiate object by giving 4 parameters
        public ParkingPermit(String make, String model, String licencePlate, String owner) {
                this.make = make;
                this.model = model;
                LicencePlate = licencePlate;
                Owner = owner;
                //setting parameters which are not given in constructor
                color="Not Defined";
                year="Not Defined";
                VIN="Not Defined";
        }
        
        //constructor with 5 parametrs, 3 mandatory and 2 optional
        //instantiate class by giving 5 parameters
        public ParkingPermit(String make, String model, String licencePlate, String color, String owner) {
                this.make = make;
                this.model = model;
                LicencePlate = licencePlate;
                this.color = color;
                Owner = owner;
                //setting parameters which are not given in constructor
                year="Not Defined";
                VIN="Not Defined";
        }
        
        //constructor with 6 parametrs, 3 mandatory and 3 optional
        //instantiate class by giving 6 parameters
        public ParkingPermit(String make, String model, String licencePlate, String color, String year, String owner) {
                this.make = make;
                this.model = model;
                LicencePlate = licencePlate;
                this.color = color;
                this.year = year;
                Owner = owner;
                //setting parameters which are not given in constructor
                VIN="Not Defined";
        }

}