170 Two Sum III - Data structure design

class TwoSum {
    
    HashMap<Integer, Integer> map;

    /** Initialize your data structure here. */
    public TwoSum() {
        map = new HashMap<>();
    }
    
    /** Add the number to an internal data structure.. */
    public void add(int number) {
        Integer freq = map.get(number);
        if(freq == null){
            map.put(number, 1);
        }else{
            map.put(number, freq + 1);
        }
    }
    
    /** Find if there exists any pair of numbers which sum is equal to the value. */
    public boolean find(int value) {
        for(int element : map.keySet()){ ///  map.keySet()
            int target = value - element;
            if(element == target && map.get(element) > 1){
              return true;
            }
            if(element != target && map.containsKey(target)){
              return true;
            }
        }
        return false;
    }
}

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.

Example 1:

add(1); add(3); add(5);
find(4) -> true
find(7) -> false

Example 2:

add(3); add(1); add(2);
find(3) -> true
find(6) -> false