350 Intersection of Two Arrays II

Given two arrays, write a function to compute their intersection.

Example:
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2, 2].

Note:
Each element in the result should appear as many times as it shows in both arrays.
The result can be in any order.
Follow up:
What if the given array is already sorted? How would you optimize your algorithm?
What if nums1’s size is small compared to nums2’s size? Which algorithm is better?
What if elements of nums2 are stored on disk, and the memory is limited such that you cannot load all elements into the memory at once?

class Solution {
  public int[] intersect(int[] nums1, int[] nums2) {
    Map<Integer, Integer> map1 = new HashMap<Integer, Integer>();
    Map<Integer, Integer> map2 = new HashMap<Integer, Integer>();

    // write numbers in nums1 in map1
    for (int n : nums1) {
      if (!map1.containsKey(n)) { map1.put(n, 1); }
      else { map1.put(n, 1 + map1.get(n)); }
    }
    // compute the count of result
    int count = 0;
    // if n in nums1 and nums2 put it in map2
    for (int n : nums2) {
      if (map1.containsKey(n)) {
        if (map2.containsKey(n)) {
          if (map1.get(n) <= map2.get(n)) { continue; }
          else { map2.put(n, 1 + map2.get(n)); count += 1;}
        } else {
          map2.put(n, 1);
          count += 1;
        }
      }
    }

    // write numbers in map2 to result
    int[] result = new int[count];
    count -= 1;
    for (Map.Entry<Integer, Integer> entry : map2.entrySet()) {
      for (int i = 0; i < entry.getValue(); i++) {
        result[count] = entry.getKey();
        count -= 1;
      }
    }
    return result;
  }
}