Counting the Number of Even and Odd Elements in an Array in Java

Understanding Even and Odd Count

This task involves counting the number of even and odd elements in an array.

We will explore three different methods to achieve this in Java.

Method 1: Using Loop

This method iterates through the array and counts even and odd elements.

public class EvenOddCount {
    public static void countEvenOdd(int[] arr) {
        int evenCount = 0, oddCount = 0;
        for (int num : arr) {
            if (num % 2 == 0)
                evenCount++;
            else
                oddCount++;
        }
        System.out.println("Even Count: " + evenCount + ", Odd Count: " + oddCount);
    }
    
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5, 6, 7, 8};
        countEvenOdd(arr);
    }
}
            

Method 2: Using Recursion

This method counts even and odd numbers using recursion.

public class EvenOddRecursion {
    public static void countEvenOddRec(int[] arr, int index, int evenCount, int oddCount) {
        if (index == arr.length) {
            System.out.println("Even Count: " + evenCount + ", Odd Count: " + oddCount);
            return;
        }
        if (arr[index] % 2 == 0)
            evenCount++;
        else
            oddCount++;
        countEvenOddRec(arr, index + 1, evenCount, oddCount);
    }
    
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5, 6, 7, 8};
        countEvenOddRec(arr, 0, 0, 0);
    }
}
            

Method 3: Using Streams

This method uses Java Streams to determine even and odd numbers.

import java.util.Arrays;

public class EvenOddStream {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3, 4, 5, 6, 7, 8};
        long evenCount = Arrays.stream(arr).filter(num -> num % 2 == 0).count();
        long oddCount = arr.length - evenCount;
        System.out.println("Even Count: " + evenCount + ", Odd Count: " + oddCount);
    }
}