# Finding Odd and Even Numbers in a Java Array

Identifying odd and even numbers is one of the fundamental concepts in programming. In Java, determining whether a number is odd or even is a straightforward task, typically done using the modulus operator. Let us delve into understanding how to work with a Java array to identify odd and even numbers.

## 1. Odd and Even Numbers and the Modulus Operator

In mathematics, an **even number** is any integer that is divisible by 2, meaning it has a remainder of 0 when divided by 2. Conversely, an **odd number** is any integer that, when divided by 2, leaves a remainder of 1. In Java, you can determine if a number is odd or even using the modulus operator (`%`

). For any number `n`

:

- If
`n % 2 == 0`

, the number is even. - If
`n % 2 != 0`

, the number is odd.

## 2. Identifying Odd and Even Numbers Using Loops

The most straightforward way to identify odd and even numbers in an array is by iterating through the array using a loop. Below is an example of how to do this using a `for`

loop.

public class OddEvenNumbers { public static void main(String[] args) { int[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; System.out.println("Even numbers:"); for (int number: numbers) { if (number % 2 == 0) { System.out.print(number + " "); } } System.out.println("\nOdd numbers:"); for (int number: numbers) { if (number % 2 != 0) { System.out.print(number + " "); } } } }

### 2.1 Code Breakdown and output

The code defines a:

- We declare an array
`numbers`

with values from 1 to 10. - We loop through the array using a
`for-each`

loop and check whether each number is even or odd using the modulus operator (`%`

). - If the number is divisible by 2, it is printed as an even number; otherwise, it is an odd number.

When the above program is executed the following output is returned on the IDE console.

Even numbers: 2 4 6 8 10 Odd numbers: 1 3 5 7 9

## 3. Identifying Odd and Even Numbers Using Streams

Java 8 introduced the Streams API, which allows for a more functional approach to processing collections of objects. Using Streams, we can filter out odd and even numbers more cleanly and concisely.

import java.util.Arrays; public class OddEvenStreams { public static void main(String[] args) { int[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; System.out.println("Even numbers:"); Arrays.stream(numbers) .filter(n -> n % 2 == 0) .forEach(n -> System.out.print(n + " ")); System.out.println("\nOdd numbers:"); Arrays.stream(numbers) .filter(n -> n % 2 != 0) .forEach(n -> System.out.print(n + " ")); } }

### 3.1 Code Breakdown and output

The code defines a:

- We use the
`Arrays.stream()`

method to create a stream from the array of numbers. - The
`filter()`

method is used to filter even numbers (`n % 2 == 0`

) and odd numbers (`n % 2 != 0`

). `forEach()`

is then used to print the filtered numbers.

When the above program is executed the following output is returned on the IDE console.

Even numbers: 2 4 6 8 10 Odd numbers: 1 3 5 7 9

## 4. Conclusion

Identifying odd and even numbers in Java is a simple task that can be approached in various ways. Using the modulus operator is the key to determining whether a number is odd or even. You can implement this logic using traditional loops or by taking advantage of Java’s functional programming features with the Streams API. Both methods are efficient and widely used in practice.