When any number which ends with 0,2,4,6,8 is divided by 2 that is an even number. And when any number ends with 1,3,5,7,9 is not divided by two is an odd number.

**Example:**

Input :8Output:Sum of First 8 Even numbers = 72 Sum of First 8 Odd numbers = 64

**Approach #1: Iterative**

- Create two variables evenSum and oddSum and initialize them by 0.
- Start For loop from 1 to 2*n.
- If i is even Add i with evenSum.
- Else add i with oddSum.
- Print evenSum and oddSum at the end of loop.

Below is the implementation of the Java program:

## Java

`// Calculate the Sum of First N Odd & Even Numbers in Java ` `import` `java.io.*; ` ` ` `public` `class` `GFG { ` ` ` ` ` `// Driver function ` ` ` `public` `static` `void` `main(String[] args) ` ` ` `{ ` ` ` `int` `n = ` `8` `; ` ` ` `int` `evenSum = ` `0` `; ` ` ` `int` `oddSum = ` `0` `; ` ` ` ` ` `for` `(` `int` `i = ` `1` `; i <= ` `2` `* n; i++) { ` ` ` `// check even & odd using Bitwise AND operator ` ` ` `if` `((i & ` `1` `) == ` `0` `) ` ` ` `evenSum += i; ` ` ` `else` ` ` `oddSum += i; ` ` ` `} ` ` ` `// Sum of even numbers less then 17 ` ` ` `System.out.println(` `"Sum of First "` `+ n ` ` ` `+ ` `" Even numbers = "` `+ evenSum); ` ` ` ` ` `// sum of odd numbers less then 17 ` ` ` `System.out.println(` `"Sum of First "` `+ n ` ` ` `+ ` `" Odd numbers = "` `+ oddSum); ` ` ` `} ` `}` |

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**Output**

Sum of First 8 Even numbers = 72 Sum of First 8 Odd numbers = 64

**Time Complexity:** O(N), where N is the number of First N even/odd numbers.

**Method 2: Using AP Formulas.**

- Sum of First N Even Numbers = n * (n+1)
- Sum of First N Odd Numbers = n * n

Below is the implementation of the above approach:

## Java

`// Calculate the Sum of First N Odd & Even Numbers in Java ` `import` `java.io.*; ` ` ` `public` `class` `GFG { ` ` ` ` ` `// Function to find the sum of even numbers ` ` ` `static` `int` `sumOfEvenNums(` `int` `n) { ` `return` `n * (n + ` `1` `); } ` ` ` ` ` `// Function to find the sum of odd numbers. ` ` ` `static` `int` `sumOfOddNums(` `int` `n) { ` `return` `n * n; } ` ` ` ` ` `// Driver function ` ` ` `public` `static` `void` `main(String[] args) ` ` ` `{ ` ` ` `int` `n = ` `10` `; ` ` ` `int` `evenSum = sumOfEvenNums(n); ` ` ` `int` `oddSum = sumOfOddNums(n); ` ` ` ` ` `// Sum of even numbers ` ` ` `System.out.println(` `"Sum of First "` `+ n ` ` ` `+ ` `" Even numbers = "` `+ evenSum); ` ` ` ` ` `// sum of odd numbers ` ` ` `System.out.println(` `"Sum of First "` `+ n ` ` ` `+ ` `" Odd numbers = "` `+ oddSum); ` ` ` `} ` `}` |

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**Output**

Sum of First 10 Even numbers = 110 Sum of First 10 Odd numbers = 100

**Time Complexity:** O(1)

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