771. Jewels and Stones

You're given strings J representing the types of stones that are jewels, and S representing the stones you have.  Each character in Sis 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".

class Solution:

    def numJewelsInStones(self, J, S):

        """

        :type J: str

        :type S: str

        :rtype: int

        """

        count = 0

        for i in range(len(S)):

            for j in range(len(J)):

                if S[i]==J[j]:

                    count+=1

        return count