Guideline: For simplicity and consistency, this course will primarily use int for integer values and double for floating point values.

Syntax for Type Casting:

(DataType)variableName
(DataType)value

Important Warning: Be cautious with type casting, as data loss may lead to inaccurate results.

double d = 4.5;
int i = (int)d;  // i = 4, but d remains 4.5

Type casting does not modify the original variable's value.

Example of boolean variable declaration:

boolean lightsOn = true;
boolean isComplete = false;

The literals true and false are reserved words and cannot be used as identifiers in your program.

Important Warning!

• ▶ The equality operator consists of two equal signs (==), not one (=). A single equal sign (=) is used for assignment.
• ▶ The result of a comparison is always a boolean value (true or false).

Example of comparison:

double radius = 1;
System.out.println(radius > 0);  // Outputs: true

Laboratory Work: Loan Payment Calculator

[File name and class name: L2Lab1.java]

User Input:
Enter annual interest rate (%): 6.5
Enter loan term (years): 15
Enter loan amount (rubles): 2000000

Program Output:
Monthly payment: 17140.12 rubles
Total loan cost: 3085221.60 rubles

How to Run Java files (even if there is no java extension) :

1. Save the file (filename.java).
2. Compile:

bash (terminal):

javac filename.java

3. Run:

bash (terminal):

java filename

Complete Solution Code:

/* Laboratory Work: Loan Payment Calculator */
import java.util.Scanner;

public class L2Lab1 {
    public static void main(String[] args) {
        // Constant: months per year
        final int MONTHS_PER_YEAR = 12;

        // Create a Scanner for user input
        Scanner scanner = ...new Scanner(System.in);

        // Step 1: get annual interest rate
        System.out.print("Enter annual interest rate (%): ");
        double annualInterestRate = scanner.nextDouble();

        // Convert to monthly fraction
        double monthlyInterestRate = annualInterestRate / 12 / 100;

        // Step 2: get loan term in years
        System.out.print("Enter loan term (years): ");
        int numberOfYears = scanner.nextInt();

        // Step 3: get loan amount
        System.out.print("Enter loan amount (rubles): ");
        double loanAmount = ...scanner.nextDouble();

        // Step 4.1: calculate monthly payment
        double monthlyPayment = ...loanAmount * monthlyInterestRate /
                (1 - 1 / Math.pow(1 + monthlyInterestRate, numberOfYears * MONTHS_PER_YEAR));

        // Step 4.2: calculate total payment
        double totalPayment = ...monthlyPayment * numberOfYears * MONTHS_PER_YEAR;

        // Round in borrower's favor (down to nearest kopeck)
        monthlyPayment = Math.floor(monthlyPayment * 100) / 100;
        totalPayment = Math.floor(totalPayment * 100) / 100;

        // Step 5: display results
        System.out.printf(..."Monthly payment: %.2f rubles%n", monthlyPayment);
        System.out.printf(..."Total loan cost: %.2f rubles%n", totalPayment);

        // Close the scanner
        ...scanner.close();
    }
}

Laboratory Work: Calculating Taxi Fare

[File name and class name: L2Lab2.java]

Input:
Enter the initial odometer reading: 13505
Enter the final odometer reading: 13810

Output:
You traveled 305 km. At a rate of 8 rubles 50 kopecks per km,
the fare is 2592 rubles 50 kopecks.

How to Run Java files (even if there is no java extension) :

1. Save the file (filename.java).
   
2. Compile:
3. Run:

bash (terminal):

javac filename.java

bash (terminal):

java filename

/* Laboratory Work: Calculating Taxi Fare */
import java.util.Scanner;

public class L2Lab2 {
    public static void main(String[] args) {
        // Constant: rate per kilometer (8 rubles 50 kopecks)
        final double RATE_PER_KM = ...8.50;

        // Create a scanner object for user input
        Scanner scanner = ...new Scanner(System.in);

        // Step 1: display the program header
        System.out.println("TAXI FARE CALCULATOR");

        // Step 2: prompt for initial odometer reading
        System.out.print("Enter the initial odometer reading: ");
        int startOdometer = ...scanner.nextInt();

        // Step 3: prompt for final odometer reading
        System.out.print("Enter the final odometer reading: ");
        ...int endOdometer = scanner.nextInt();

        // Step 4: calculate the distance traveled
        int distance = ...endOdometer - startOdometer;

        // Step 5: compute the trip cost
        double totalCost = ...distance * RATE_PER_KM;

        // Step 6: display the result
        System.out.println("You traveled " + distance + " km. At a rate of 8 rubles 50 kopecks per km,");
        System.out.printf("the fare is %.0f rubles %.0f kopecks.%n",
                Math.floor(totalCost), (totalCost - Math.floor(totalCost)) * 100);

        // Close the scanner
        ...
        scanner.close();
    }
}

Lab 3: Boolean Type and Double Inequality

Objective: Check if double inequality A < B < C is true for three given integers. Note: Do not use the conditional operator.

[File name and class name: L2Lab3.java]

Input three numbers, please
5  7  10
The result: true
---
Input three numbers, please
8  7  10
The result: false

Algorithm:

1. Open Visual Studio Code.
2. Create a new file named L2Lab3.java.
3. Import the Scanner library: import java.util.Scanner;
4. Inside the main function, ask user to input three numbers.
5. Create a Scanner object: Scanner scanner = new Scanner(System.in);
6. Read three integers using Scanner methods.
7. Use logical operator && to check double inequality: a < b && b < c
8. Output the result directly without using conditional operator.
   

   
   How to Run Java files (even if there is no java extension) :

• Save the file (filename.java).
• Compile:
• Run:

bash (terminal):

javac filename.java

bash (terminal):

java filename

/* Lab 3: Check if A < B < C for three integers */
import java.util.Scanner;

public class L2Lab3 {
    public static void main(String[] args) {
        // Create Scanner object for input
        Scanner scanner = new Scanner(System.in);
        
        // Ask user for input
        System.out.println("Input three numbers, please");
        
        // Read three integers
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int c = scanner.nextInt();
        
        // Check double inequality using logical AND operator
        boolean result = (a < b) && (b < c);
        
        // Output the result (no conditional operator used)
        System.out.println("The result: " + result);
        
        // Alternative: output with formatted message
        System.out.printf("Double inequality %d < %d < %d is %b%n", a, b, c, result);
        
        // Close the scanner
        scanner.close();
    }
}

Task 1: Compare Sums of Number Pairs

Objective: Four integers are given. Check if sum of first two numbers is greater than sum of next two numbers. Output the result as true or false directly without using conditional operator.

Expected output:

Please, input four integers:
5  7  10  4
5 + 7 > 10 + 4 : false
---
Please, input four integers:
8  7  10  2
8 + 7 > 10 + 2 : true

[File name and class name: L2Task1.java]

/* Task 3: Check if (x1 + x2) > (x3 + x4) */
import java.util.Scanner;

public class L1Task1 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        System.out.println("Please, input four integers:");
        int x1 = scanner.nextInt();
        int x2 = scanner.nextInt();
        int x3 = scanner.nextInt();
        int x4 = scanner.nextInt();
        
        // Calculate sums and compare
        int sum1 = x1 +  x2;
        int sum2 = x3 + x4;
        boolean result = sum1 > sum2;
        
        System.out.println("The result: " + result);
        System.out.printf("(%d+%d) > (%d+%d) = %b%n", x1, x2, x3, x4, result);
        
        scanner.close();
    }
}