Java Code Example: find pairs with target sum

In this code example, the findPairs method takes an integer array arr and an integer target as input and returns a list of pairs (Pair class) containing the elements that sum up to the target value.

The algorithm uses two nested loops to iterate over all possible pairs of elements. The outer loop selects the first element, and the inner loop iterates over the remaining elements to find a matching pair.

For each pair of elements, the algorithm checks if their sum is equal to the target value. If a pair is found, it is added to the pairs list.

In the main method, an example input array arr and target value target are defined. The findPairs method is called to find the pairs that sum up to the target value, and the resulting pairs are printed to the console.

import java.util.ArrayList;
import java.util.List;

public class PairSumFinder {
    public static List<Pair<Integer, Integer>> findPairs(int[] arr, int target) {
        List<Pair<Integer, Integer>> pairs = new ArrayList<>();

        // Iterate over all possible pairs of elements
        for (int i = 0; i < arr.length; i++) {
            for (int j = i + 1; j < arr.length; j++) {
                if (arr[i] + arr[j] == target) {
                    pairs.add(new Pair<>(arr[i], arr[j]));

        return pairs;

    public static void main(String[] args) {
        int[] arr = {2, 4, 5, 3, 6, 8};
        int target = 9;
        List<Pair<Integer, Integer>> result = findPairs(arr, target);

        System.out.println("Pairs that sum up to " + target + " are:");
        for (Pair<Integer, Integer> pair : result) {
            System.out.println("(" + pair.getKey() + ", " + pair.getValue() + ")");

    // Custom Pair class to hold pair of values
    static class Pair<K, V> {
        private K key;
        private V value;

        public Pair(K key, V value) {
            this.key = key;
            this.value = value;

        public K getKey() {
            return key;

        public V getValue() {
            return value;