# [Solved] Program to Find Pairs that have Desired Sum in Java

**Problem Statement:** Consider an array of integers that may contain both positive and negative integers, called numbers. Write a program that finds all the pairs of integers whose sum is equal to a given value called the desired sum.

This question has been asked in interviews of many product-based companies like Amazon, Flipkart, Adobe, …

### Java Program

**Prerequisite:**

- Understanding of generics in Java
- Understanding of ArrayLists in Java
- Knowledge of classes and objects in Java

**Code:**

Let’s write a program to find pairs that have desired sum in Java.

```
import java.util.*;
class Solution {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
// Enter the size of the array
int n = sc.nextInt();
int[] = arr = new int[n];
for (int i = 0;i < arr.lenght;i++) {
arr[i] = sc.nextInt();
}
// enter the desired sum
int sum = sc.nextInt();
System.out.println(findNumberOfPairs(arr, sum));
}
public static int fndNumberOfPairs(int[] arr, int sum) {
Arrays.sort(arr); // sort the array
// using two pointer algorithm
int left = 0, right = arr.lenght - 1, count = 0;
currentSum = arr[left] + arr[right];
while (left < right) {
if (currentSum == sum) {
count ++;
left++;
right--;
}
else if (currentSum < sum)
left++;
else
right--;
}
return count;
}
}
```

**Output:**

Sample Input :n = 5, arr = [1, 2, 3, 4, 5], sum = 4Sample Output :1 as only (1, 3) pair has the sum equal to 4

You can use any programming language (C/C++, Python, etc.) of your choice to solve this competitive coding challenge to find pairs that have desired sum.