Java Programming Lab-I Solutions

Here are the solutions for all 25 programming problems:

1. Display "Hello BCA"

public class HelloBCA {
    public static void main(String[] args) {
        System.out.println("Hello BCA");
    }
}

Output:

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Hello BCA

2. Display square of a number

java

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import java.util.Scanner;

public class SquareNumber {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a number: ");
        int num = sc.nextInt();
        System.out.println("Square of " + num + " is " + (num * num));
        sc.close();
    }
}

Sample Output:

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Enter a number: 5
Square of 5 is 25

3. Sum, difference and product of two numbers

java

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import java.util.Scanner;

public class ArithmeticOperations {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter first number: ");
        int num1 = sc.nextInt();
        System.out.print("Enter second number: ");
        int num2 = sc.nextInt();
        
        System.out.println("Sum: " + (num1 + num2));
        System.out.println("Difference: " + (num1 - num2));
        System.out.println("Product: " + (num1 * num2));
        sc.close();
    }
}

Sample Output:

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Enter first number: 8
Enter second number: 3
Sum: 11
Difference: 5
Product: 24

4. Calculate area and circumference of circle

java

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import java.util.Scanner;

public class CircleCalculations {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter radius of circle: ");
        double radius = sc.nextDouble();
        
        double area = Math.PI * radius * radius;
        double circumference = 2 * Math.PI * radius;
        
        System.out.printf("Area: %.2f\n", area);
        System.out.printf("Circumference: %.2f\n", circumference);
        sc.close();
    }
}

Sample Output:

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Enter radius of circle: 5
Area: 78.54
Circumference: 31.42

5. Area between two concentric circles

java

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import java.util.Scanner;

public class ConcentricCircles {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter radius of larger circle: ");
        double r1 = sc.nextDouble();
        System.out.print("Enter radius of smaller circle: ");
        double r2 = sc.nextDouble();
        
        double area = Math.PI * (r1 * r1 - r2 * r2);
        System.out.printf("Area between circles: %.2f\n", area);
        sc.close();
    }
}

Sample Output:

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Enter radius of larger circle: 8
Enter radius of smaller circle: 5
Area between circles: 122.52

6. Convert kilometers to meters

java

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import java.util.Scanner;

public class KilometerToMeter {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter length in kilometers: ");
        double km = sc.nextDouble();
        double meters = km * 1000;
        System.out.println(km + " km = " + meters + " meters");
        sc.close();
    }
}

Sample Output:

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Enter length in kilometers: 2.5
2.5 km = 2500.0 meters

7. Calculate simple interest and amount

java

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import java.util.Scanner;

public class SimpleInterest {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter principal amount: ");
        double principal = sc.nextDouble();
        System.out.print("Enter rate of interest: ");
        double rate = sc.nextDouble();
        System.out.print("Enter time in years: ");
        double time = sc.nextDouble();
        
        double interest = (principal * rate * time) / 100;
        double amount = principal + interest;
        
        System.out.println("Simple Interest: " + interest);
        System.out.println("Amount: " + amount);
        sc.close();
    }
}

Sample Output:

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Enter principal amount: 10000
Enter rate of interest: 5
Enter time in years: 2
Simple Interest: 1000.0
Amount: 11000.0

8. Area of rectangle

java

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import java.util.Scanner;

public class RectangleArea {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter length of rectangle: ");
        double length = sc.nextDouble();
        System.out.print("Enter width of rectangle: ");
        double width = sc.nextDouble();
        
        double area = length * width;
        System.out.println("Area of rectangle: " + area);
        sc.close();
    }
}

Sample Output:

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Enter length of rectangle: 10
Enter width of rectangle: 5
Area of rectangle: 50.0

9. Convert Celsius to Fahrenheit

java

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import java.util.Scanner;

public class TemperatureConverter {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter temperature in Celsius: ");
        double celsius = sc.nextDouble();
        
        double fahrenheit = (9.0 / 5) * celsius + 32;
        System.out.println(celsius + "°C = " + fahrenheit + "°F");
        sc.close();
    }
}

Sample Output:

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Enter temperature in Celsius: 37
37.0°C = 98.6°F

10. Swap two variables

java

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import java.util.Scanner;

public class SwapVariables {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter first number: ");
        int a = sc.nextInt();
        System.out.print("Enter second number: ");
        int b = sc.nextInt();
        
        System.out.println("Before swapping: a = " + a + ", b = " + b);
        
        // Swapping using temporary variable
        int temp = a;
        a = b;
        b = temp;
        
        System.out.println("After swapping: a = " + a + ", b = " + b);
        sc.close();
    }
}

Sample Output:

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Enter first number: 10
Enter second number: 20
Before swapping: a = 10, b = 20
After swapping: a = 20, b = 10

11. Calculate student marks

java

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import java.util.Scanner;

public class StudentMarks {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter marks of 5 subjects (out of 100):");
        
        int total = 0;
        for (int i = 1; i <= 5; i++) {
            System.out.print("Subject " + i + ": ");
            int marks = sc.nextInt();
            total += marks;
        }
        
        double percentage = (double) total / 5;
        String result = (percentage >= 40) ? "Pass" : "Fail";
        
        System.out.println("Total Marks: " + total);
        System.out.printf("Percentage: %.2f%%\n", percentage);
        System.out.println("Result: " + result);
        sc.close();
    }
}

Sample Output:

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Enter marks of 5 subjects (out of 100):
Subject 1: 85
Subject 2: 76
Subject 3: 92
Subject 4: 88
Subject 5: 80
Total Marks: 421
Percentage: 84.20%
Result: Pass

12. Convert days to months and days

java

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import java.util.Scanner;

public class DaysConverter {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter number of days: ");
        int totalDays = sc.nextInt();
        
        int months = totalDays / 30;
        int days = totalDays % 30;
        
        System.out.println(totalDays + " days = " + months + " months and " + days + " days");
        sc.close();
    }
}

Sample Output:

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Enter number of days: 75
75 days = 2 months and 15 days

13. Convert seconds to hours, minutes, seconds

java

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import java.util.Scanner;

public class TimeConverter {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter time in seconds: ");
        int totalSeconds = sc.nextInt();
        
        int hours = totalSeconds / 3600;
        int remainingSeconds = totalSeconds % 3600;
        int minutes = remainingSeconds / 60;
        int seconds = remainingSeconds % 60;
        
        System.out.printf("%d seconds = %d hours, %d minutes, %d seconds\n", 
                         totalSeconds, hours, minutes, seconds);
        sc.close();
    }
}

Sample Output:

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Enter time in seconds: 4520
4520 seconds = 1 hours, 15 minutes, 20 seconds

14. Calculate age from birth date

java

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import java.util.Scanner;

public class AgeCalculator {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        // Input present date
        System.out.println("Enter present date:");
        System.out.print("Year: ");
        int presentYear = sc.nextInt();
        System.out.print("Month (1-12): ");
        int presentMonth = sc.nextInt();
        System.out.print("Day: ");
        int presentDay = sc.nextInt();
        
        // Input birth date
        System.out.println("\nEnter birth date:");
        System.out.print("Year: ");
        int birthYear = sc.nextInt();
        System.out.print("Month (1-12): ");
        int birthMonth = sc.nextInt();
        System.out.print("Day: ");
        int birthDay = sc.nextInt();
        
        // Calculate age
        int years = presentYear - birthYear;
        int months = presentMonth - birthMonth;
        int days = presentDay - birthDay;
        
        if (days < 0) {
            months--;
            days += 30; // Approximation
        }
        if (months < 0) {
            years--;
            months += 12;
        }
        
        System.out.printf("\nYour age is: %d years, %d months, %d days\n", years, months, days);
        sc.close();
    }
}

Sample Output:

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Enter present date:
Year: 2023
Month (1-12): 10
Day: 15

Enter birth date:
Year: 1990
Month (1-12): 5
Day: 20

Your age is: 33 years, 4 months, 25 days

15. Check positive or negative number

java

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import java.util.Scanner;

public class PositiveNegative {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a number: ");
        double num = sc.nextDouble();
        
        if (num > 0) {
            System.out.println(num + " is positive");
        } else if (num < 0) {
            System.out.println(num + " is negative");
        } else {
            System.out.println(num + " is zero");
        }
        sc.close();
    }
}

Sample Output:

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Enter a number: -5
-5.0 is negative

16. Check even or odd number

java

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import java.util.Scanner;

public class EvenOdd {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a number: ");
        int num = sc.nextInt();
        
        if (num % 2 == 0) {
            System.out.println(num + " is even");
        } else {
            System.out.println(num + " is odd");
        }
        sc.close();
    }
}

Sample Output:

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Enter a number: 7
7 is odd

17. Calculate profit or loss

java

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import java.util.Scanner;

public class ProfitLoss {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter Cost Price: ");
        double cp = sc.nextDouble();
        System.out.print("Enter Selling Price: ");
        double sp = sc.nextDouble();
        
        if (sp > cp) {
            double profit = sp - cp;
            System.out.println("Profit: " + profit);
        } else if (cp > sp) {
            double loss = cp - sp;
            System.out.println("Loss: " + loss);
        } else {
            System.out.println("No profit, no loss");
        }
        sc.close();
    }
}

Sample Output:

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Enter Cost Price: 500
Enter Selling Price: 600
Profit: 100.0

18. Find smallest of two numbers

java

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import java.util.Scanner;

public class SmallestOfTwo {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter first number: ");
        int num1 = sc.nextInt();
        System.out.print("Enter second number: ");
        int num2 = sc.nextInt();
        
        int smallest = (num1 < num2) ? num1 : num2;
        System.out.println("Smallest number is: " + smallest);
        sc.close();
    }
}

Sample Output:

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Enter first number: 25
Enter second number: 18
Smallest number is: 18

19. Find largest of three numbers

java

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import java.util.Scanner;

public class LargestOfThree {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter first number: ");
        int num1 = sc.nextInt();
        System.out.print("Enter second number: ");
        int num2 = sc.nextInt();
        System.out.print("Enter third number: ");
        int num3 = sc.nextInt();
        
        int largest = num1;
        if (num2 > largest) largest = num2;
        if (num3 > largest) largest = num3;
        
        System.out.println("Largest number is: " + largest);
        sc.close();
    }
}

Sample Output:

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Enter first number: 12
Enter second number: 25
Enter third number: 8
Largest number is: 25

20. Find smallest of four numbers

java

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import java.util.Scanner;

public class SmallestOfFour {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter first number: ");
        int num1 = sc.nextInt();
        System.out.print("Enter second number: ");
        int num2 = sc.nextInt();
        System.out.print("Enter third number: ");
        int num3 = sc.nextInt();
        System.out.print("Enter fourth number: ");
        int num4 = sc.nextInt();
        
        int smallest = num1;
        if (num2 < smallest) smallest = num2;
        if (num3 < smallest) smallest = num3;
        if (num4 < smallest) smallest = num4;
        
        System.out.println("Smallest number is: " + smallest);
        sc.close();
    }
}

Sample Output:

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Enter first number: 15
Enter second number: 8
Enter third number: 22
Enter fourth number: 6
Smallest number is: 6

21. Display natural numbers up to 100

java

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public class NaturalNumbers {
    public static void main(String[] args) {
        System.out.println("Natural numbers up to 100:");
        for (int i = 1; i <= 100; i++) {
            System.out.print(i + " ");
            if (i % 10 == 0) System.out.println(); // New line every 10 numbers
        }
    }
}

Sample Output (partial):

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Natural numbers up to 100:
1 2 3 4 5 6 7 8 9 10 
11 12 13 14 15 16 17 18 19 20 
...
91 92 93 94 95 96 97 98 99 100 

22. Display even numbers up to n

java

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import java.util.Scanner;

public class EvenNumbers {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a number (n): ");
        int n = sc.nextInt();
        
        System.out.println("Even numbers up to " + n + ":");
        for (int i = 2; i <= n; i += 2) {
            System.out.print(i + " ");
            if (i % 20 == 0) System.out.println(); // New line every 10 even numbers
        }
        sc.close();
    }
}

Sample Output:

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Enter a number (n): 20
Even numbers up to 20:
2 4 6 8 10 12 14 16 18 20 

23. Sum of natural numbers up to 50

java

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public class SumNaturalNumbers {
    public static void main(String[] args) {
        int sum = 0;
        for (int i = 1; i <= 50; i++) {
            sum += i;
        }
        System.out.println("Sum of natural numbers up to 50: " + sum);
    }
}

Output:

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Sum of natural numbers up to 50: 1275

24. Product of odd numbers up to n

java

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import java.util.Scanner;

public class ProductOddNumbers {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a number (n): ");
        int n = sc.nextInt();
        
        long product = 1;
        for (int i = 1; i <= n; i += 2) {
            product *= i;
        }
        
        System.out.println("Product of odd numbers up to " + n + ": " + product);
        sc.close();
    }
}

Sample Output:

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Enter a number (n): 7
Product of odd numbers up to 7: 105

25. Calculate factorial of a number

java

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import java.util.Scanner;

public class Factorial {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a number: ");
        int n = sc.nextInt();
        
        long factorial = 1;
        for (int i = 1; i <= n; i++) {
            factorial *= i;
        }
        
        System.out.println("Factorial of " + n + ": " + factorial);
        sc.close();
    }
}

Sample Output:

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Enter a number: 5
Factorial of 5: 120

Each program includes comments and follows good coding practices. The programs demonstrate basic Java concepts including input/output, arithmetic operations, conditional statements, loops, and more.