L8R.java

//q1
Question#1 (Constructors):
        1. Create a class called Rectangle that contains the following data fields:
        • height as integer.
        • width as integer.
        2. The class also contains the following methods:
        • A no-arguments constructor that initializes Rectangle data fields to their default values.
        • A two-arguments constructor that initializes Rectangle data fields to specific given values.
        • A method named getArea() that returns the area of the rectangle.
        3. In the main method:
        • Create an object (r1) with its default values
        • Create an object (r2) of the Rectangle class with width=10 and height =20.
        • Print the area of the rectangle r1 by invoking getArea().

public class Rectangle {
    private int height;
    private int width;

    // No-arguments constructor
    public Rectangle() {
        height = 0;
        width = 0;
    }

    // Two-arguments constructor
    public Rectangle(int width, int height) {
        this.width = width;
        this.height = height;
    }

    public int getArea() {
        return width * height;
    }

    public static void main(String[] args) {
        // Create an object with default values
        Rectangle r1 = new Rectangle();

        // Create an object with specific values
        Rectangle r2 = new Rectangle(10, 20);

        // Print the area of r1
        System.out.println("Area of r1: " + r1.getArea());
    }
}


question 2
        Question#2 (Access Modifies, Mutators and Accessors):
        1. Create a class called Student that contains the following data fields:
        • name as private String.
        • stdno as private integer.
        • grade as private integer.
        2. The class also contains the following methods:
        • A no-argument constructor to initialize the Student data fields to its default values.
        • Set and get methods for all data fields.
        o setGrade method will check if the grade is less than 40 it will be set to 40,
        otherwise the grade will be the same.

        • classifyGrade method that has no argument and returns the appropriate letter for the
        grade according to the following:
        80 - 100 --------- A
        50 – 79 ---------- B
< 50 -------------- F
        • print method that prints the Student data fields and the grade letter (invoke classifyGrade
        method).
        3. In the main method :
        • Create an object (s1) of the Student class with name ="Ahmad", ID= 123415, grade=85
        • Invoke classifyGrade method and print the corresponding grade letter for s1.
        • Print all student information.

public class Student {
    private String name;
    private int stdno;
    private int grade;

    // No-arguments constructor
    public Student() {
        name = "";
        stdno = 0;
        grade = 0;
    }

    // Set methods
    public void setName(String name) {
        this.name = name;
    }

    public void setStdNo(int stdno) {
        this.stdno = stdno;
    }

    public void setGrade(int grade) {
        if (grade < 40) {
            this.grade = 40;
        } else {
            this.grade = grade;
        }
    }

    // Get methods
    public String getName() {
        return name;
    }

    public int getStdNo() {
        return stdno;
    }

    public int getGrade() {
        return grade;
    }

    // Classify the grade and return the appropriate letter
    public String classifyGrade() {
        if (grade >= 80 && grade <= 100) {
            return "A";
        } else if (grade >= 50 && grade <= 79) {
            return "B";
        } else {
            return "F";
        }
    }

    // Print student information
    public void print() {
        System.out.println("Name: " + name);
        System.out.println("Student Number: " + stdno);
        System.out.println("Grade: " + grade);
        System.out.println("Grade Letter: " + classifyGrade());
    }

    public static void main(String[] args) {
        // Create an object of the Student class with specific values
        Student s1 = new Student();
        s1.setName("Ahmad");
        s1.setStdNo(123415);
        s1.setGrade(85);

        // Print the grade letter for s1
        System.out.println("Grade Letter for s1: " + s1.classifyGrade());

        // Print all student information
        s1.print();
    }
}
Question#3 (Instance variables and static variables):
        1. Create a class called Account that contains the following data fields:
        • num as a static private integer
        • id as private integer.
        • balance as private double.
        2. The class also contains the following methods:
        • A no-arguments constructor that
        o initializes data fields to their default values
        o increments num and assigns the new num to the id.
        • The set and get methods for id and balance data fields.
        • Static set and get method for num data field.
        • A method called withdraw(double) that withdraws a specified amount from the account
        balance. Before withdraw, the method should check whether the available balance is
        sufficient.
        • A method named deposit(double) that deposits a specified amount to the account
        balance.
        3. In the main method :
        • Create an object (a1) of the Account class with balance=1000.
        • Create an object (a2) of the Account class with balance=2000.
        • Print id and balance of a1 and a2.
        • Withdraw 100 from a1 balance.
        • Deposit 50 to a1 balance.
        • Print the balance of a1 and a2.
        • Print the total number of the created accounts

public class Account {
    private static int num;
    private int id;
    private double balance;

    // Static set and get methods for num
    public static void setNum(int num) {
        Account.num = num;
    }

    public static int getNum() {
        return num;
    }

    // No-arguments constructor
    public Account() {
        id = ++num;
        balance = 0.0;
    }

    // Set and get methods for id and balance
    public void setId(int id) {
        this.id = id;
    }

    public int getId() {
        return id;
    }

    public void setBalance(double balance) {
        this.balance = balance;
    }

    public double getBalance() {
        return balance;
    }

    // Method to withdraw from the account balance
    public void withdraw(double amount) {
        if (balance >= amount) {
            balance -= amount;
            System.out.println("Withdrawn: " + amount);
        } else {
            System.out.println("Insufficient balance");
        }
    }

    // Method to deposit into the account balance
    public void deposit(double amount) {
        balance += amount;
        System.out.println("Deposited: " + amount);
    }

    public static void main(String[] args) {
        // Create objects of the Account class
        Account a1 = new Account();
        a1.setBalance(1000);

        Account a2 = new Account();
        a2.setBalance(2000);

        // Print id and balance of a1 and a2
        System.out.println("a1 - ID: " + a1.getId() + ", Balance: " + a1.getBalance());
        System.out.println("a2 - ID: " + a2.getId() + ", Balance: " + a2.getBalance());

        // Withdraw 100 from a1 balance
        a1.withdraw(100);

        // Deposit 50 to a1 balance
        a1.deposit(50);

        // Print the balance of a1 and a2
        System.out.println("a1 - Balance: " + a1.getBalance());
        System.out.println("a2 - Balance: " + a2.getBalance());

        // Print the total number of created accounts
        System.out.println("Total number of accounts: " + Account.getNum());
    }
}