Find Two Array Elements Having Maximum Product in Java?

Two elements giving the maximum product in an array means, we have to find two largest array elements which will eventually give the maximum product possible.

In this article we will see how we can find the maximum product of two elements in Java.

To show you some instances

Instance-1

Suppose we have the below array

[10, 2, 3, -5, 99, 12, 0, -1]

In this array the largest element is 99 and second largest is 12.

Max product = 99 * 12

Hence the maximum product of two elements in this array is 1188.

Instance-2

Suppose we have the below array

[6, 1, 2, 4, 3, 5, 9]

In this array the largest element is 9 and the second largest is 6.>

Max product = 9 * 6

Hence the maximum product of two elements in this array is 54.

Instance-3

Suppose we have the below array

[10, 17, 14, 12, 15, 6, 5, 19]

In this array the largest element is 19 and the second largest is 17.

Max product= 19 * 17

Hence the maximum product of two elements in this array is 323.

Algorithm

Algorithm-1

Step 1 − Use a for loop to find the largest and second largest element in the array.

Step 2 − Find their product.

Step 3 − Print the product.

Algorithm-2

Step 1 − Sort the array elements.

Step-2 − Take the last and second last element of the array.

Step 3 −Find their product.

Step 4 −Print the product.

Syntax

To sort the array we need to use the sort( ) method of the Arrays class of java.util package.

Following is the syntax to sort any array in ascending order using the method-

Arrays.sort(array_name);

Where, ‘array_name’ refers to the array that you want to sort.

Multiple Approaches

We have provided the solution in different approaches.

• Find The Largest Product Using for Loop.

• Find The Largest Product Using Arrays.sort.

Let’s see the program along with its output one by one.

Approach-1: By Using for Loop

In this approach, we use a for loop to iterate through the array elements to find out the largest and second largest element. These two elements will give the maximum product.

Example

public class Main {
   public static void main(String[] args) {
      
      // The array elements
      int arr[] = { 10, 2, 3, -5, 99, 12, 0, -1 };
     
      // Storing the first element in both variables
      int first = arr[0], second = arr[0];
     
      // For loop to iterate the elements from 1 to n
      // to find the first largest element
      for (int i = 0; i < arr.length; i++) {
        
         // If array element is larger than current largest element, then swap
         if (arr[i] > first)
            first = arr[i];
      }
      
      // For loop to iterate the elements from 1 to n
      // to find the second largest element
      for (int i = 0; i < arr.length; i++) {

         // If array element is larger than current largest element and not equals to
         // largest element, then swap
         if (arr[i] > second && arr[i] != first)
            second = arr[i];
      }
      
      // Print the product
      System.out.println("Largest product = " + (first * second));
      System.out.println("The elements are " + first + " and " + second);
   }
}

Output

Largest product = 1188
The elements are 99 and 12

Approach-2: By Using Arrays.sort

In this approach, we sort the array using the Arrays.sort( ) method. Then we take the elements at last and second last index. As the array was sorted already, these two elements will give the maximum product.

Example

import java.util.Arrays;

public class Main{
   public static void main(String[] args) {
     
      // The array elements
      int arr[] = { 10, 2, 3, -5, 9, 12, 0, -1 };
     
      // Sort the array using the sort method from array class
      Arrays.sort(arr);
     
      // Storing the last element as largest and second last element as second largest
      int first = arr[arr.length - 1], second = arr[arr.length - 2];
      
      // Print the maximum product
      System.out.println("Maximum product = " + (first * second));
      System.out.println("The elements are " + first + " and " + second);
   }
}

Output

Maximum product = 120
The elements are 12 and 10

In this article, we explored different approaches to find two elements in an array with maximum product in Java.