For this problem, you are not allowed to use arrays, and the only string methods you are allowed to use are .equals, .length, .charAt, and .substring. Write a method that returns the number of times the single-character string 'ltr' occurs in a string 'str', except do not count 'ltr' if it occurs immediately after the single-character string 'exclude'. For example, in the string "this that then the other thing" if 'ltr' is "t" and 'exclude' is " " the method should return 3 since there are three occurrences of 't' that do not occur immediately after a space. Your method should be case-sensitive, so "t" and "T" are not considered the same character. As a pre-condition, you may assume that 'ltr' and 'exclude' will each contain exactly one character. Look at the test data!