Two Sum III

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

public class TwoSum {
    private HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
    /** Initialize your data structure here. */
    public TwoSum() {
        
    }
    
    /** Add the number to an internal data structure.. */
    public void add(int number) {
        map.put(number, map.containsKey(number) ? map.get(number) + 1 : 1);
    }
    
    /** Find if there exists any pair of numbers which sum is equal to the value. */
    public boolean find(int value) {
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            int base = entry.getKey();
            int findMe = value - base;
            
            if ((base == findMe && map.get(base) >= 2) || 
                 base != findMe && map.containsKey(findMe))
                 return true;
        }
        return false;
    }
}

/**
 * Your TwoSum object will be instantiated and called as such:
 * TwoSum obj = new TwoSum();
 * obj.add(number);
 * boolean param_2 = obj.find(value);
 */