LeetCode 170 - Two Sum III - Data structure design

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

Map<Integer, Integer> dict = new HashMap<Integer, Integer>();

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

public boolean find(int value) {
	for (Integer key : dict.keySet()) {
		if (value - key == key) {
			if (dict.get(key) >= 2) {
				return true;
			}
		} else if (dict.containsKey(value - key)) {
			return true;
		}
	}

	return false;
}