Find Missing Number In An ArrayList

import java.util.ArrayList;

public class MissingNumberInArrayList {

// We find out sum of ‘n’ numbers by using formula n*(n+1)/2.
static int sumOfNnumbers(int n) {
int sum = (n * (n + 1)) / 2;
return sum;
}

//we will find sum of all elements of array list
static int sumOfElements(ArrayList<Integer> list) {
int sum = 0;

for (int i = 0; i < list.size(); i++) {
sum = sum + list.get(i);
}
return sum;
}

// Another Approach, It will find multiple missing elements

static ArrayList<Integer> findMissingElements(ArrayList<Integer> oldList,
int numbers) {
ArrayList<Integer> newList = new ArrayList<Integer>(numbers);

for (int i = 1; i <= numbers; i++) {
newList.add(i);
}

newList.removeAll(oldList);
return newList;
}

public static void main(String[] args) {
int numbers = 10;

ArrayList<Integer> list = new ArrayList<Integer>();
for (int i = 1; i <= numbers; i++) {
if (i != 5)     // Skip one number
list.add(i);
}

System.out.println(list);

int sumOfNnumbers = sumOfNnumbers(numbers);

int sumOfElements = sumOfElements(list);

//Missing_Number = (Sum of 1 to ‘n’ numbers) – (Sum of elements of array list )

int missingNumber = sumOfNnumbers - sumOfElements;

System.out.println("Missing Number is = " + missingNumber);

// Another Approach

System.out.println("Missing Numbers are = "
+ findMissingElements(list, numbers));
}
}

Fizz Buzz Problem In Java

Write a program in java which prints the numbers from 1 to 100. But, multiples of 3 should be replaced with “Fizz”, multiples of 5 should be replaced with “Buzz” and multiples of both 3 and 5 should be replaced with “FizzBuzz”?

public class FizzBuzzProblem
{
    public static void main(String args[])
    {
        for(int i = 1; i <= 100; i++)
        {
            if((i % (3*5)) == 0)             //if ((i % 3) == 0 && (i % 5) == 0) 
            {
                System.out.println("FizzBuzz");
            }
            else if ((i % 5) == 0)
            {
                System.out.println("Buzz");
              }
            else if ((i % 3) == 0)
            {
                System.out.println("Fizz");
            }
            else
            {
                System.out.println(i);
              }
        }
    }

}