Building an Aircraft Hierarchy: From Automobiles to Airbuses in Java

Explanation For Automobile Constructor Code 

1)public class Automobile {: This line declares a class named Automobile. The public keyword indicates that the class is accessible from other classes. Classes are templates for objects, defining their behavior and properties.

2)Automobile(){: This line declares a constructor method for the Automobile class. Constructors are special methods used for initializing objects of a class. This constructor has the same name as the class (Automobile) and no parameters, making it a default constructor.

3)System.out.println("Automobile( ) invoked");: This line prints the message "Automobile( ) invoked" to the console when the constructor is invoked. It provides feedback indicating that the constructor has been called and executed.

public class Automobile {
   
    Automobile(){
        System.out.println("Automobile( ) invoked");
    }
}

Conclusion:
The provided code defines a Java class named Automobile with a default constructor. When an object of this class is created, the constructor prints a message to the console indicating that it has been invoked. This class serves as a basic template for creating automobile objects in a Java program.

Explanation For class Plane which extends Automobile 

1)public class Plane extends Automobile {: This line declares a new class named Plane that extends the Automobile class. It means that Plane inherits all the attributes and methods of the Automobile class.

2)Plane(){: This line declares a default constructor for the Plane class. It is invoked when a Plane object is created without any arguments.

3)System.out.println("Plane() invoked");: This line prints a message to the console indicating that the default constructor of the Plane class has been invoked.

4)Plane (int numberOfEngines){: This line declares a parameterized constructor for the Plane class that takes an integer parameter numberOfEngines. It is invoked when a Plane object is created with an integer argument.

5)System.out.println("Plane(x) invoked");: This line prints a message to the console indicating that the parameterized constructor of the Plane class has been invoked.

public class Plane extends Automobile {
   
    Plane(){
        System.out.println("Plane() invoked");
    }


    Plane (int numberOfEngines){
        System.out.println("Plane(x) invoked");
    }
}

These lines of code define a Java class named Plane that inherits from the Automobile class. It provides two constructors: a default constructor and a parameterized constructor that takes an integer argument. When a Plane object is created using the default constructor, it prints a message indicating that the default constructor has been invoked. Similarly, when a Plane object is created using the parameterized constructor, it prints a message indicating that the parameterized constructor has been invoked. This class structure enables flexibility in creating Plane objects with or without specifying the number of engines.

public class Airbus extends Plane {
    
    Airbus(){
        super(4);
        System.out.println("Airbus() invoked");
    }
}

Explanation For class Airbus with a default constructor which extends Plane 

1)public static void main(String[] args) {: This line is the entry point of the Java program. It defines a method named main which is public (accessible from anywhere), static (can be called without creating an instance of the class), returns void (does not return any value), and takes an array of String arguments as input (args). This is where the program execution begins.

2)Airbus airbus = new Airbus();: This line creates a new instance of the Airbus class using the default constructor.

3)Airbus is the data type of the variable airbus, representing the class type.

4)airbus is the name of the variable that holds the reference to the newly created Airbus object.

5)new Airbus() instantiates a new object of the Airbus class by calling its default constructor.

public class Runner {
   
    public static void main(String[] args) {
       
        Airbus airbus=new Airbus();

    }
}

The main method serves as the entry point for the Java program.
Airbus airbus = new Airbus(); creates a new Airbus object and assigns it to the variable airbus.
This line demonstrates object instantiation, where the Airbus class's default constructor is invoked to create a new instance of the class.
Overall, this code initializes a new Airbus object, which can then be used to access its properties and methods.