Chapter 12, Problem 7E

Write a program that will read sentences from a text file, placing each sentence in its own instance of ArrayList. (You will create a sentence object by adding words to it one at a time as they are read.) When a sentence has been completely read, add the sentence to another instance of ArrayList. Once you have read the entire file, you will have an instance of ArrayList that contains several instances of ArrayList, one for each sentence read. Now ask the user to enter a sentence number and a word number. Display the word that occurs in the given position. If the sentence number or word number is not valid, provide an appropriate error message.