To better understand the object-creation process, let’s begin with a simple case of two-level inheritance, where we have just a base class and its derived class. When we create an instance of a derived class, it contains an object of its base class. This base class object is the same as the one we would have created by directly instantiating the base class itself. The derived class object is just a wrapper on this base class object. It is essential that the base class object be properly initialized. This can be ensured only if we know for sure that during the object-creation process the constructor of the base class is called—remember from our previous discussions that a class constructor has all the appropriate knowledge and privileges to perform its initialization. Thus, the compiler automatically inserts calls to the base class constructor in the derived class constructor provided we do not call super explicitly.

To explain the object-creation process, we will use the inheritance

hierarchy defined in our asset management system shown here.

Each of the three classes in this figure has an additional operation defined— and that is the class constructor. The printDescription method of the original Asset class is removed for simplicity. The constructor in all three cases does not take any arguments. The purpose of this no-arguments construct is to announce whenever the corresponding class is instantiated.

To keep things simple and focus on the aspects of object creation, we cover only the implementation code for the no-arguments constructor for each of these classes. The constructor prints a message to the user whenever the class is instantiated. The main program creates an object of SavingsAccount. This, in turn, creates objects of its superclasses, as we will see very shortly when we study the output of the program.

Super Class- Asset

class Asset
 {
                     private int id;
                     private String type;

                     public Asset()
                             {
                             System.out.println("Creating Asset ...");
                     }

}

class BankAccount extends Asset {
                     private String bankName;
                     private int accountNumber;
                     private float balance;

                     public BankAccount() {
                             System.out.println("Creating BankAccount ...");
                     }

}

class SavingsAccount extends BankAccount {
                     private float interestRate;
 
                     public SavingsAccount() {
                             System.out.println("Creating SavingsAccount ...");

                     }

}

public class ObjectCreationProcess {

                     public static void main(String[] args) {
                             SavingsAccount tomSavingsAccount = new SavingsAccount();

                     }
}

Creating Asset ...

Creating BankAccount ...

Creating SavingsAccount ...

public SavingsAccount() {
super();
System.out.println("Creating SavingsAccount ...");
}