Java Programming Day 2

☕ Java Day 2 – Exploring Math, Formatting, and Financial Calculations

Welcome back to my Java Learning Series!
Today was Day 2, and I dived into the Math class, explored number formatting using printf(), and even implemented real-world calculators like compound interest, hypotenuse, and circle geometry formulas.

This session helped me understand how Java can be used for real-world applications in fields like finance, engineering, and data representation.

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🔢 1. Java Math Functions Practice

✅ Program:

javaCopyEditpublic class MathPractice {
   public static void main(String[] args) {
      System.out.println(Math.abs(-6));         // Absolute value
      System.out.println(Math.ceil(4.5));       // Rounds up
      System.out.println(Math.floor(4.5));      // Rounds down
      System.out.println(Math.round(4.4));      // Nearest int
      System.out.println(Math.max(3, 9));       // Max value
      System.out.println(Math.min(3, 9));       // Min value
      System.out.println(Math.sqrt(36));        // Square root
      System.out.println(Math.pow(2, 3));       // Power
   }
}

📘 Notes & What I Learned:

These functions are extremely useful in scientific, statistical, and financial calculations.

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📐 2. Hypotenuse Calculator

✅ Program:

javaCopyEditimport java.util.Scanner;

public class HypotenuseCalculator {
   public static void main(String[] args) {
      Scanner scanner = new Scanner(System.in);

      System.out.print("Enter side A: ");
      double a = scanner.nextDouble();

      System.out.print("Enter side B: ");
      double b = scanner.nextDouble();

      double c = Math.sqrt(Math.pow(a, 2) + Math.pow(b, 2));
      System.out.println("The hypotenuse is: " + c);
      scanner.close();
   }
}

📘 Notes:

• Applied the Pythagorean Theorem:
  c=a2+b2c = \sqrt{a^2 + b^2}c=a2+b2​

• Used Math.pow() to square each side and Math.sqrt() to find the hypotenuse.

• This program is useful in geometry, physics, and game development where calculating distances is common.

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🌐 3. Circle Area, Circumference, and Volume

✅ Program:

javaCopyEditimport java.util.Scanner;

public class CircleMath {
   public static void main(String[] args) {
      Scanner scanner = new Scanner(System.in);
      double pi = Math.PI;

      System.out.print("Enter the radius (cm): ");
      double radius = scanner.nextDouble();

      double area = pi * Math.pow(radius, 2);
      double circumference = 2 * pi * radius;
      double volume = (4.0 / 3) * pi * Math.pow(radius, 3);

      System.out.printf("Area = %.2f cm²\n", area);
      System.out.printf("Circumference = %.2f cm\n", circumference);
      System.out.printf("Volume = %.2f cm³\n", volume);

      scanner.close();
   }
}

📘 Notes:

• Math.PI gives us an accurate value of π.

• Math.pow() handles exponentiation.

• printf("%.2f", value) was used for formatting up to 2 decimal places.

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🎯 4. Number Formatting with printf()

✅ Program:

javaCopyEditpublic class FormatPractice {
   public static void main(String[] args) {
      double price1 = 9.99;
      double price2 = 100.15;
      double price3 = -54.01;
      double price4 = 9000.99;
      double price5 = 1000000.15;
      double price6 = -5400000.01;

      int a = 1;
      int c = 663;

      System.out.printf("%.1f\n", price1);           // One decimal
      System.out.printf("%.2f\n", price2);           // Two decimals
      System.out.printf("%.3f\n", price3);           // Three decimals
      System.out.printf("%+.1f\n", price4);          // Show + sign
      System.out.printf("%,.2f\n", price5);          // Comma separator
      System.out.printf("%(.2f\n", price6);          // Negative in ()
      System.out.printf("% .1f\n", price6);          // Space for sign
      System.out.printf("%04d\n", a);                // Pad with zeros
      System.out.printf("%04d\n", c);
      System.out.printf("%4d\n", a);                 // Right aligned
      System.out.printf("%4d\n", c);
      System.out.printf("%-4d\n", c);                // Left aligned
   }
}

📘 Notes:

Such formatting is essential in financial reports, invoices, tables, and data presentation.

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💸 5. Compound Interest Calculator

✅ Program:

javaCopyEditimport java.util.Scanner;

public class CompoundInterest {
   public static void main(String[] args) {
      Scanner scanner = new Scanner(System.in);
      double principle, rate, amount;
      int timesCompounded, years;

      System.out.print("Enter the principle amount : ");
      principle = scanner.nextDouble();

      System.out.print("Enter the interest rate (in %) : ");
      rate = scanner.nextDouble() / 100;

      System.out.print("Enter the number of times compounded per year : ");
      timesCompounded = scanner.nextInt();

      System.out.print("Enter the # of years : ");
      years = scanner.nextInt();

      amount = principle * Math.pow(1 + rate / timesCompounded, timesCompounded * years);

      System.out.printf("The amount after %d years is : $%.2f", years, amount);
      scanner.close();
   }
}

🧮 Formula Used:

Amount=P×(1+RN)N×T\text{Amount} = P \times \left(1 + \frac{R}{N}\right)^{N \times T}Amount=P×(1+NR​)N×T

Where:

• P = Principal

• R = Annual Interest Rate

• N = Number of times interest is compounded per year

• T = Number of years

📘 Notes:

• A practical financial application.

• Used Math.pow() for exponentiation and printf() for clean currency formatting.

• This calculator can be extended to banking software or investment planning tools.

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✅ Final Summary

✨ What I Achieved Today:

✔ Explored Java’s Math class to simplify complex calculations
✔ Applied geometry formulas in real-time programs
✔ Created a compound interest calculator – useful in finance
✔ Practiced formatting output like a pro with printf()
✔ Enhanced understanding of Java syntax, logic, and real-world utility