Design and implement a TwoSum class. It should support the following operations: add and find.

TwoSumFileStructure.java

/**
Design and implement a TwoSum class. It should support the following operations: add and find.

add - Add the number to an internal data structure. find - Find if there exists any pair of numbers which sum is equal to the value.

For example,
add(1); add(3); add(5);
find(4) -> true
find(7) -> false
**/

import java.util.HashMap;
import java.util.Map;

public class TwoSumDS {
    private Map<Integer, Integer> map = new HashMap<>();

    public void add(int n) {
        if (map.containsKey(n)) {
            map.put(n, map.get(n) + 1);
        } else {
            map.put(n, 1);
        }
    }

    public boolean find(int target) {
        // check to see if map has any elements
        for (int n : map.keySet()) {
            int minus = map.get(target - n);
            if (map.containsKey(minus)) {
                if (minus == n) // if there are two identical numbers like 2+2 = 4
                    return map.get(n) > 1; // Is there more than value of n?
                return true; // for all other cases where minus =m
            }
        }
        return false;

    }
}