Question

Write a program that inputs a sentence from the user (assume no punctuation), then determines and displays the unique words in alphabetical order. Treat uppercase and lowercase letters the same.

Short answer

To solve the exercise, the program should prompt for a sentence, lower the case, split the sentence into words, discard duplicates using a set, sort the words alphabetically, and then display them.

Step-by-step solution

Request User Input

Prompt the user to input a sentence. Ensure to notify the user to input text without punctuation and inform that uppercase and lowercase letters will be treated equally.

Convert to Lowercase

Convert the entire input sentence to lowercase to normalize the case, as the program is case-insensitive.

Split the Sentence into Words

Use a string method to split the sentence into a list of individual words.

Create a Set to Store Unique Words

Initialize an empty set which will be used to store unique words. Sets automatically remove duplicates.

Add Words to the Set

Iterate through the list of words and add each word to the set. This will ensure only unique words are kept.

Sort the Unique Words

Convert the set back to a list and use a sorting function to sort the words in alphabetical order.

Display the Unique Words

Print the sorted list of unique words to the user.

Key concepts

String Manipulation in Java

String manipulation is an essential concept in Java programming that involves altering, parsing, or inspecting strings - sequences of characters such as words or sentences. In our exercise, string manipulation is vital to organize unique words from user input.

Common string manipulation techniques include converting strings to lowercase or uppercase, splitting strings, trimming whitespaces, and more. In the given exercise, to perform case-insensitive comparisons, the first step is to convert the user input to lowercase using methods like toLowerCase(). This standardizes every character for uniform processing.

Another critical manipulation is splitting the sentence into words. Java provides the split() method for strings, which divides a sentence based on a specified delimiter, typically a space character (' '), and returns an array of substrings. In this context, each word becomes an element of the array.

User Input Handling in Java

Handling user input is a routine requirement in many Java applications, allowing for dynamic and interactive programs. The Java Scanner class is a common way to obtain input from users.

When implementing user input handling, it's important to offer clear instructions, as seen in the exercise where the user is prompted to enter a sentence without punctuation. Conveying these details ensures that the program receives the expected format, reducing errors and misunderstandings.

Once the input is accepted, it's crucial to validate and process it appropriately. In the context of our exercise, the input is processed by normalizing the case and then segregating words, which are strings, to be worked on by the program.

Data Structures in Java

Data structures are a way of organizing and storing data so that it can be accessed and modified efficiently. In Java, arrays, lists, sets, and maps are examples of commonly used data structures.

In the given exercise, the unique nature of a set is exploited because a set automatically ensures that only distinct elements are stored - an essential feature when we need to extract unique words from a list of potentially repeated words. The implementation involves creating a HashSet and adding words to it, where duplicated entries are inherently filtered out.

However, sets do not maintain any particular order. To display the words alphabetically, we convert the set back into a list - a data structure that can be sorted. Java's Collections.sort() method or the ArrayList.sort() method can then be used to organize the list of unique words before presenting the results to the user.