leetcode 771. Jewels and Stones

Seawolf

You're given strings J representing the types of stones that are jewels, and S representing the stones you have.  Each character in S is a type of stone you have.  You want to know how many of the stones you have are also jewels.

The letters in J are guaranteed distinct, and all characters in J and S are letters. Letters are case sensitive, so "a" is considered a different type of stone from "A".

Example 1:

Input: J = "aA", S = "aAAbbbb"
Output: 3
Example 2:

Input: J = "z", S = "ZZ"
Output: 0
Note:

S and J will consist of letters and have length at most 50.
The characters in J are distinct.

class Solution {
    public int numJewelsInStones(String J, String S) {
        
        if(S.length() == 0) return 0;
        
        char[] charArray = S.toCharArray();
        int count = 0;
        
        for(char i : charArray){
            
            if(J.indexOf(i) != -1){
                
                count++;
            }
        }
        
        return count;
    }
}