Finding Pairs With a Certain Sum.java

class FindSumPairs {

    private int [] nums1;
    private int [] nums2;
    Map<Integer, Integer> map = new HashMap<>();
    public FindSumPairs(int[] nums1, int[] nums2) {
        this.nums1 = nums1;
        this.nums2 = nums2;
        for (int number : nums2) {
            map.put(number, map.getOrDefault(number, 0) + 1);
        } 
        
    }
    
    public void add(int index, int val) {
        map.put(nums2[index], map.get(nums2[index]) - 1);
        nums2[index] += val;
        map.put(nums2[index], map.getOrDefault(nums2[index], 0) + 1);
    }
    
    public int count(int tot) {
        int result = 0;
        for (int number : nums1) {
            if (map.containsKey(tot - number)) {
                result += map.get(tot - number);
            }
        }
        return result;
    }
}

/**
 * Your FindSumPairs object will be instantiated and called as such:
 * FindSumPairs obj = new FindSumPairs(nums1, nums2);
 * obj.add(index,val);
 * int param_2 = obj.count(tot);
 */