CODEWITHSUNDEEP
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Daniel_Kamel
Daniel_Kamel

Reputation: 619

Should I create a List of Objects or change my interface?

I have 3 classes that implement the following interface:

public interface PolicyType {
    public boolean isValid();
    public void displayTemplate();
}

And in my main I have created and initialized 1 instance of each class:

//the same method exists for MedicalPolicy and MotorPolicy
private static void displaySucMsg(TravelPolicy travelPolicy,List<TravelPolicy> travelPolicyList){
        if(travelPolicy.isValid()) {
            System.out.println("Policy: " + travelPolicy.getPolicyNo() + " was added successfully");
            travelPolicyList.add(travelPolicy);
        }
}

public static void main(String[] args){
        List<TravelPolicy> travelPolicyList = new ArrayList<TravelPolicy>(2);
        List<MotorPolicy> motorPolicyList = new ArrayList<MotorPolicy>(2);
        List<MedicalPolicy> medicalPolicyList = new ArrayList<MedicalPolicy>(2);

        TravelPolicy travelPolicy1 = new TravelPolicy(policyNo,param2,etc...);

        displaySucMsg(travelPolicy1,travelPolicyList);

        MotorPolicy motorPolicy = new MotorPolicy(policyNo,param2,etc...);

        displaySucMsg(motorPolicy,motorPolicyList);

        MedicalPolicy medicalPolicy = new MedicalPolicy(policyNo,param2,etc...);

        displaySucMsg(medicalPolicy,medicalPolicyList);
    }

As you can see I've created 3 Lists each one for a class but I want to have 1 List so that at the end I can use a for loop on it, my problem is that the displaySucMsg uses a getter method for the policyNo field (and then add the instance to the appropriate List) so I can't create a List of PolicyType and add all instances to it.

My question is should I create a List of Object (which I assume would be a bad practice) and add all 3 Lists to it, or should I add public String getPolicyNo() to my interface since all my 3 classes have that method (which I assume is also a bad practice since if I ever created a new class that implement PolicyType but doesn't need a getPolicyNo() method would be very bad), or should I just leave my code as it is and run 1 for loop on each List or is there another solution?

Upvotes: 0

Views: 72

Answers (1)

Salim
Salim

Reputation: 2178

The class design should reflect the real life business scenario. So define what is a "policy" and what are its mandatory properties and behavior of this object. If policyNo and policyType are important properties then don't worry about they being empty ever.

If it ever happens that a property was thought to be mandatory but with changing business scenario it is no longer that case then you can always implement it and return a default value or actually have a default implementation on the interface. You can even bring in 2 interfaces - OldPolicy and NewPolicy to accommodate the change in definition of "policy".

In your example add getPolicyNo() to interface PolicyType and build a List which can hold objects of 3 policy types.

Upvotes: 1

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