Write a program that will read a line of text that ends with a period, which serves as a sentinel value. Display all the letters that occur in the text, one per line and in alphabetical order, along with the number of times each letter occurs in the text. Use an array of base type int of length 26, so that the element at index 0 contains the number of a’s, the element at index 1 contains the number of b’s, and so forth. Allow both uppercase and lowercase letters as input, but treat uppercase and lowercase versions of the same letter as being equal. Use one of the methods toUpperCase or toLowerCase in the wrapper class Character, described in Chapter 6. You will find it helpful to define a method that takes a character as an argument and returns an int value that is the correct index for that character. For example, the argument 'a' results in 0 as the return value, the argument 'b' gives 1 as the return value, and so on. Note that you can use a type cast, such as (int)letter, to change a char to an int. Of course, this will not get the number you want, but if you subtract (int)'a', you will then get the right index. Allow the user to repeat this task until the user says she or he is through.