1. Fibonacci series without using recursion
2. Fibonacci series using recursion

• Program:

class Main {
  public static void main(String[] args) {

    int n = 10, firstTerm = 0, secondTerm = 1;
    System.out.println("Fibonacci Series till " + n + " terms:");

    for (int i = 1; i <= n; ++i) {
      System.out.print(firstTerm + ", ");

      // compute the next term
      int nextTerm = firstTerm + secondTerm;
      firstTerm = secondTerm;
      secondTerm = nextTerm;
    }
  }
}

• Output:

Fibonacci Series till 10 terms:
0, 1, 1, 2, 3, 5, 8, 13, 21, 34,

• Program:

public class MultiplicationTable {

    public static void main(String[] args) {

        int num = 8;
        for(int i = 1; i <= 10; ++i)
        {
            System.out.printf("%d * %d = %d \n", num, i, num * i);
        }
    }
}

• Output:

8 * 1 = 8 
8 * 2 = 16 
8 * 3 = 24 
8 * 4 = 32
8 * 5 = 40
8 * 6 = 48
8 * 7 = 56
8 * 8 = 64
8 * 9 = 72
8 * 10 = 80

• Program:

import java.math.BigInteger;

public class Factorial {

    public static void main(String[] args) {

        int num = 11;
        BigInteger factorial = BigInteger.ONE;
        for(int i = 1; i <= num; ++i)
        {
            // factorial = factorial * i;
            factorial = factorial.multiply(BigInteger.valueOf(i));
        }
        System.out.printf("Factorial of %d = %d", num, factorial);
    }
}

Factorial of 11 = 39916800

• Java program to find the sum of the first 100 natural numbers
• Java program to find the sum of n natural numbers
• Java program to find the sum of n natural numbers using the function

• Program:

public class SumNatural {

    public static void main(String[] args) {

        int num = 110, sum = 0;

        for(int i = 1; i <= num; ++i)
        {
            // sum = sum + i;
            sum += i;
        }

        System.out.println("Sum = " + sum);
    }
}

• Output:

Sum = 6105

• Program:

public class Alphabet {

    public static void main(String[] args) {

        char c = '-';

        if( (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'))
            System.out.println(c + " is an alphabet.");
        else
            System.out.println(c + " is not an alphabet.");
    }
}

• Output:

- is not an alphabet.

----- OR -----

n is an alphabet.

----- OR -----

V is an alphabet.

• If a number is less than zero, then it is a negative number
• If a number is greater than zero, then it is a negative number
• If a number is equal to zero, then it is neither negative nor positive number

• Program:

public class PositiveNegative {

    public static void main(String[] args) {

        double number = 11.1;

        // true if number is less than 0
        if (number < 0.0)
            System.out.println(number + " is a negative number.");

        // true if number is greater than 0
        else if ( number > 0.0)
            System.out.println(number + " is a positive number.");

        // if both test expression is evaluated to false
        else
            System.out.println(number + " is 0.");
    }
}

• Output:

11.1 is a positive number.

----- OR -----

-11.1 is a negative number.

• Program:

public class MultiplyTwoNumbers {

    public static void main(String[] args) {

        float first = 3.4f;
        float second = 1.5f;

        float product = first * second;

        System.out.println("The product is: " + product);
    }
}

• Output:

The product is: 5.1

• A century year is a year ending with 00.  A century year is a leap year only if it is divisible by 400.
• A leap year (except a century year) can be identified if it is exactly divisible by 4.
• A century year should be divisible by 4 and 100 both.
• A non-century year should be divisible only by 4.

• Program:

public class Main {

  public static void main(String[] args) {

    // year to be checked
    int year = 2011;
    boolean leap = false;

    // if the year is divided by 4
    if (year % 4 == 0) {

      // if the year is century
      if (year % 100 == 0) {

        // if year is divided by 400
        // then it is a leap year
        if (year % 400 == 0)
          leap = true;
        else
          leap = false;
      }
      
      // if the year is not century
      else
        leap = true;
    }
    
    else
      leap = false;

    if (leap)
      System.out.println(year + " is a leap year.");
    else
      System.out.println(year + " is not a leap year.");
  }
}

• Output:

2011 is not a leap year

--- Another example ---

2012 is a leap year

• if determinant > 0, roots are real and different
• if determinant < 0, roots are complex and different
• if determinant == 0, roots are real and equal

• Program:

public class Main {

  public static void main(String[] args) {

    // value a, b, and c
    double a = 4.6, b = 2, c = 4.2;
    double root1, root2;

    // calculate the determinant (b2 - 4ac)
    double determinant = b * b - 4 * a * c;

    // check if determinant is greater than 0
    if (determinant > 0) {

      // two real and distinct roots
      root1 = (-b + Math.sqrt(determinant)) / (2 * a);
      root2 = (-b - Math.sqrt(determinant)) / (2 * a);

      System.out.format("root1 = %.2f and root2 = %.2f", root1, root2);
    }

    // check if determinant is equal to 0
    else if (determinant == 0) {

      // two real and equal roots
      // determinant is equal to 0
      // so -b + 0 == -b
      root1 = root2 = -b / (2 * a);
      System.out.format("root1 = root2 = %.2f;", root1);
    }

    // if determinant is less than zero
    else {

      // roots are complex number and distinct
      double real = -b / (2 * a);
      double imaginary = Math.sqrt(-determinant) / (2 * a);
      System.out.format("root1 = %.2f+%.2fi", real, imaginary);
      System.out.format("\nroot2 = %.2f-%.2fi", real, imaginary);
    }
  }
}

• Output:

root1 = -0.22+0.93i
root2 = -0.22-0.93i