Program 1:

Class Fundamentals, Object Creation, this, and finalize()

A) Develop a Java program to demonstrate class fundamentals, including object creation, method implementation, and constructor usage. Utilize features like the this keyword and the finalize() method.

// Demonstrate class fundamentals in Java
class Box {
    double width;
    double height;
    double depth;

    // Constructor using 'this' keyword
    Box(double width, double height, double depth) {
        this.width = width;
        this.height = height;
        this.depth = depth;
    }

    // Method to calculate and return volume
    double volume() {
        return width * height * depth;
    }

    // Finalize method called before object is destroyed
    @Override
    protected void finalize() {
        System.out.println("Box object is being destroyed.");
    }
}

public class BoxDemo {
    public static void main(String[] args) {
        // Create objects of Box
        Box myBox1 = new Box(10, 20, 15);
        Box myBox2 = new Box(3, 6, 9);

        // Get volume of first box
        double vol = myBox1.volume();
        System.out.println("Volume of myBox1 is: " + vol);

        // Get volume of second box
        vol = myBox2.volume();
        System.out.println("Volume of myBox2 is: " + vol);

        // Hint for garbage collector (not guaranteed)
        myBox1 = null;
        myBox2 = null;

        // Request garbage collection
        System.gc(); // finalize() may be called, but not immediately or reliably
    }
}

Output:

Volume of myBox1 is: 3000.0
Volume of myBox2 is: 162.0
Box object is being destroyed.
Box object is being destroyed.

Assign Values and Compute Volume in main Without Constructor

B) Write a java program with a class called box and has three variables width, height and depth assign the value 100 to width, 200 to height, 150 to depth. Compute the volume in the main class.

class Box {
    double height;
    double width;
    double depth;
}

class BoxDemo {
    public static void main(String[] args) {
        Box mybox1 = new Box();
        mybox1.height = 100;
        mybox1.width = 200;
        mybox1.depth = 150;

        double volume = mybox1.height * mybox1.width * mybox1.depth;
        System.out.println("Volume is: " + volume);
    }
}

Output:

Volume is : 3000000.0

Constructor-Based Initialization & Volume Calculation in Method

C) Create a main class BoxDemo2 create a another class Box with three instance variables where the dimensions are automatically initialized when the object is constructed. The volume must be calculated in Box class and displayed in BoxDemo2 class.

class Box {
    double height;
    double width;
    double depth;

    // Constructor initializes the dimensions
    Box() {
        height = 20;
        width = 30;
        depth = 25;
    }

    // Method to calculate volume
    double vol() {
        return height * width * depth;
    }
}

class BoxDemo2 {
    public static void main(String[] args) {
        Box mybox = new Box();
        System.out.println("Volume is: " + mybox.vol());
    }
}

Output:

Volume is :15000.0