class Solution {
    public int numJewelsInStones(String J, String S) {
        HashSet<Character> set = new HashSet<>();
        
        for(char c:J.toCharArray())
            set.add(c);
        
        int count = 0;
        for(char c:S.toCharArray())
            if(set.contains(c))
                count++;
        
        return count;
    }
}