Magic Square

public class Magic {

      private int size = 3;

      public static void main(String[] args) {

            Magic magic = new Magic(1);

            magic.magic(1);

      }

      public Magic (int size) {

            setSize(2 * size + 1);

      }

     

      public void magic(int num) {

            int limit = getLimit();

            int current = getSize() / 2;

            int[] a = new int[limit];

            a[current] = num;

            int next = 0;

            for (int i = num + 1; i < num + limit; i++) {

                  next = next(current);

                  if (a[next] == 0) {

                        a[next] = i;

                  } else {

                        next = down(current);

                        a[next] = i;

                  }

                  current = next;

            }

            display(a);

      }

     

      public void display(int[] a){

            for(int i=0; i

                  if(i%getSize()==0){

                        System.out.println();

                  }

                  System.out.printf("%5d", a[i]);

            }

                 

      }

      public int next(int i) {

            return right(up(i));

      }

      public int up(int i) {

            i = i - getSize();

            if (i < 0) {

                  i += getLimit();

            }

            return i;

      }

      public int down(int i) {

            i = i + getSize();

            if (i > getLimit()) {

                  i -= getLimit();

            }

            return i;

      }

      public int right(int i) {

            i = i + 1;

            if (i % getSize() == 0) {

                  i = i - getSize();

            }

            return i;

      }

      public int left(int i) {

            if (i % getSize() == 0) {

                  i = i + getSize() - 1;

            } else {

                  i = i - 1;

            }

            return i;

      }

      public int getSize() {

            return size;

      }

      public void setSize(int size) {

            this.size = size;

      }

      public int getLimit() {

            return getSize() * getSize();

      }

}

Checking Prime in java

      public class Prime {

            public boolean isPrime(int n) {

                  if (n < 2) {

                      return false;

                  }

                  if (n == 2) {

                      return true;

                  }

                  if (n % 2 == 0) {

                      return false;

                  }

                  int sqrt = (int) Math.sqrt(n);

                  for (int i = 3; i <= sqrt; i += 2) {

                        if (n % i == 0) {

                           return false;

                        }

                  }

                  return true;

            }

      }

String Pallendrom Checking in Java

public class Pallendrom {

      public boolean isPallendrom(String str) {

            char[] chars = str.toCharArray();

            int lchar = chars.length;

            for(int i=0; i<lchar/2; i++){

                  if(chars[i]!=chars[lchar-1-i]){

                        return false;

                  }

            }

            return true;

      }

      public static void main(String[] args) {

            String a = "12321";

            Pallendrom p = new Pallendrom();

            if(p.isPallendrom(a)){

                  System.out.println(a + " is Pallendrom.");

            }else{

                  System.out.println(a + " is not Pallendrom.");

            }

      }

}

Number Pallendrom checking in java

public class Pallendrom {

      public boolean isPallendrom(int num) {

            int tmp = num;

            int rem = 0;

            int sum = 0;

            while (tmp > 0) {

                  rem = tmp % 10;

                  sum = sum * 10 + rem;

                  tmp = tmp / 10;

            }

            return (sum == num);

      }

      public static void main(String[] args) {

            int a = 12321;

            Pallendrom p = new Pallendrom();

            if(p.isPallendrom(a)){

                  System.out.println(a + " is Pallendrom.");

            }else{

                  System.out.println(a + " is not Pallendrom.");

            }

      }

}

Finding Square root without using sqrt function in java

public class Maths {

      public double sqrt(double number) {

            if (number < 0) {

                  return Double.NaN;

            }

            if (number == 0) {

                  return number;

            }

            double epsilon = 1e-15;

            double root = 0;

            double sqrt = number;

            while (Math.abs(sqrt - (root = (number / sqrt))) > epsilon * sqrt) {

                  sqrt = (root + sqrt) / 2.0;

            }

            return sqrt;

      }

      public static void main(String[] args) {

            double num = 2;

            Maths m = new Maths();

            double sqrt = m.sqrt(num);

            System.out.println("SQRT is " + sqrt);

      }

}

LCM implementation in Java

public class Maths {

      public int lcm(int num1, int num2) {

            if (num1 == 0 || num2 == 0) {

                  return 0;

            }

            if (num1 < num2) {

                  num1 = num1 ^ num2;

                  num2 = num1 ^ num2;

                  num1 = num1 ^ num2;

            }

            int num = num1 % num2;

            if (num == 0) {

                  return num1;

            }

            for (int i = 2; i <= num; i++) {

                  if ((num1 * i) % num2 == 0) {

                        return i * num1;

                  }

            }

            return num1 * num2;

      }

      public static void main(String[] args) {

            int a = 24;

            int b = 16;

            Maths m = new Maths();

            int l = m.lcm(a, b);

            System.out.println("LCM is " + l);

      }

}

GCD implementation in Java

public class Maths {

      public int gcd(int p, int q) {

            if (q == 0){

                  return p;

            }

            return gcd(q, p % q);

      }

      public static void main(String[] args) {

            int a = 36;

            int b = 48;

           

            Maths m = new Maths();

            int g = m.gcd(a,b);

            System.out.println("GCD is " + g);

      }

}

Factorial in Java

public class Factorial {

      public static void main(String[] args) {

            Factorial f = new Factorial();

            int num = 6;

            int fact = f.factorial(6);

            System.out.println(num + " factorial is " + fact);

      }

      public int factorial(int n) {

            if (n == 1)

                  return 1;

            return n * factorial(n - 1);

      }

}