Write a method in Java named letterCount(String s, String c) which takes a string s and a letter c (which is also a string of length 1), and returns the number of times the given letter occurs in the given string. You may assume the length of the letter is exactly 1, but the first string may be empty (of zero length).

Examples: letterCount("abc-123-abc-ABC", "b") returns 2 letterCount("This is interesting!", "z") returns 0 letterCount("", "q") returns 0