Common Elements Between Two Arrays Java Program

Write a Program to Find Common Elements Between Two Arrays Java Program 

Java Program:

Write a program to find common elements between two arrays?

Description:

Write a program to identify common elements or numbers between
two given arrays. You should not use any inbuilt methods are list to
find common values.

Code:

package com.java2novice.algos;

public class CommonElementsInArray {

    public static void main(String a[]){
        int[] arr1 = {4,7,3,9,2};
        int[] arr2 = {3,2,12,9,40,32,4};
        for(int i=0;i<arr1.length;i++){
            for(int j=0;j<arr2.length;j++){
                if(arr1[i]==arr2[j]){
                    System.out.println(arr1[i]);
                }
            }
        }
    }
}

Output:

4
3
9
2

Here's a Java program that finds the common elements between two arrays:

import java.util.HashSet;

import java.util.Scanner;

public class CommonElements {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);

        

        // Input first array

        System.out.print("Enter the size of the first array: ");

        int size1 = scanner.nextInt();

        int[] array1 = new int[size1];

        System.out.println("Enter elements of the first array:");

        for (int i = 0; i < size1; i++) {

            array1[i] = scanner.nextInt();

        }

        

        // Input second array

        System.out.print("Enter the size of the second array: ");

        int size2 = scanner.nextInt();

        int[] array2 = new int[size2];

        System.out.println("Enter elements of the second array:");

        for (int i = 0; i < size2; i++) {

            array2[i] = scanner.nextInt();

        }

        

        // Find common elements

        HashSet<Integer> commonElements = findCommonElements(array1, array2);

        

        // Display common elements

        System.out.println("Common elements between the two arrays: " + commonElements);

        

        scanner.close();

    }

    public static HashSet<Integer> findCommonElements(int[] array1, int[] array2) {

        HashSet<Integer> set1 = new HashSet<>();

        HashSet<Integer> commonSet = new HashSet<>();

        // Add elements of the first array to the set

        for (int num : array1) {

            set1.add(num);

        }

        // Check for common elements in the second array

        for (int num : array2) {

            if (set1.contains(num)) {

                commonSet.add(num);

            }

        }

        return commonSet;

    }

}

Explanation:

1. Input:

   • The program first takes the size and elements of the first array.
   • Then it takes the size and elements of the second array.

2. Finding Common Elements:

   • A HashSet is used to store elements from the first array.
   • As the program iterates over the second array, it checks if each element is present in the first array's set.
   • If present, it adds that element to the commonSet.

3. Output:

   • Finally, the program prints the common elements found in both arrays.

Example:

If you input:

• First array: [1, 2, 3, 4]
• Second array: [3, 4, 5, 6]

The output will be:

Common elements between the two arrays: [3, 4]