Question

(Displaying Strings in Uppercase and Lowercase) Write an application that inputs a line of text and outputs the text twice- -once in all uppercase letters and once in all lowercase letters.

Short answer

To display a string in both uppercase and lowercase, take user input, use string methods to change the case, and then output both versions.

Step-by-step solution

Input the line of text

Prompt the user to enter a line of text. Store the user's input in a variable.

Convert to uppercase

Use a string method to convert the entire line of text to uppercase and store it in a new variable.

Convert to lowercase

Use a string method to convert the entire line of text to lowercase and store it in another new variable.

Output the results

Print the uppercase version of the text followed by the lowercase version of the text to the user.

Key concepts

Java Text Input

Handling text input in Java is a fundamental skill that enables programs to interact with users. To get started, Java provides several methods to read user input, but one of the most common and straightforward ways is to use the Scanner class from the java.util package.

To use the Scanner, you must first import it at the beginning of your code with the statement import java.util.Scanner;. After that, you can create a Scanner object to read from various input sources, including the keyboard. For reading a line of text from the user, you would typically use the nextLine() method of the Scanner object like this:

• Create a Scanner object: Scanner scanner = new Scanner(System.in);
• Prompt the user for input.
• Read the input string: String userInput = scanner.nextLine();

Once you have the input stored in a variable, you can process it as needed by your program. Being familiar with handling text input is pivotal for creating interactive Java applications.

String to Uppercase

After obtaining the user input in Java, you may want to format or manipulate it. One common task is converting a String to uppercase. This can help normalize the text for searching, sorting, or simply for display purposes. In Java, this is easily accomplished using the toUpperCase() method that is available to all String objects.

To use this method, you invoke it on a String instance and it returns a new String where all original characters have been converted to their uppercase equivalent. The original String remains unchanged as Strings in Java are immutable. Here's a quick example:

• String upperCaseText = userInput.toUpperCase();

Note that this method is locale-sensitive; it might produce unexpected results if the text contains locale-specific characters. By default, it uses the default locale, but you can also specify a Locale if needed.

String to Lowercase

Similarly, Java offers the ability to convert a String to lowercase using the toLowerCase() method. Converting a String to lowercase is commonly done when you want to make the text case-insensitive, for instance during comparisons or when storing user input for consistency.

Similar to the toUpperCase() method, toLowerCase() also returns a new String, leaving the original unaltered. Using the method looks like this:

• String lowerCaseText = userInput.toLowerCase();

Again, this method considers the locale. For languages where case conversions depend on the context, this method might not produce accurate results in every situation, and you may need to use locale-specific methods. For most use cases, however, toLowerCase() works as expected and is a simple, yet powerful tool for String manipulation in Java.