Replace lower-case characters with upper-case in Java

Hey there, future coding maestro! Ready to dive into the world of Java and explore how to swap letter cases? Today, we’re going to crack the code on a neat little trick: creating a Java Program to replace lower-case characters with upper-case and vice-versa. Doesn’t that sound exciting? Not only is this concept fundamental in programming, but it’s also a handy skill for manipulating text data. Whether you’re customizing user inputs or dabbling with file content, mastering this topic will give you an edge. So, stick around and let’s walk through it step-by-step—it’s easier than you think!

Code Example: Switching Lowercase to Uppercase and Vice-Versa in Java

import java.util.Scanner;

public class CaseConverter {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        System.out.println("Enter a string to convert: ");
        String inputString = scanner.nextLine();
        
        StringBuilder convertedString = new StringBuilder(inputString.length());
        
        for (char c : inputString.toCharArray()) {
            if (Character.isLowerCase(c)) {
                convertedString.append(Character.toUpperCase(c));
            } else if (Character.isUpperCase(c)) {
                convertedString.append(Character.toLowerCase(c));
            } else {
                convertedString.append(c);
            }
        }
        
        System.out.println("Converted string: " + convertedString);
    }
}

Explanation of the Code

Let’s decode what’s happening in the Java Program to replace lower-case characters with upper-case and vice-versa. Here’s a breakdown of the code:

We start by importing the Scanner class. This handy tool allows us to read input from the user. Pretty essential, right

The main method kicks off the program. It’s like the author of the novel—we can’t start without it
We ask the user for a string. This sets the stage for our conversion magic.

A StringBuilder called convertedString is initialized to efficiently build our new transformed string.
The code loops through each character of the user-input string. Character checks are done to see if it’s lower-case or upper-case.
If it’s lower-case, it transforms to upper-case, and vice-versa. Characters that aren’t letters remain unchanged

Finally, the converted string is printed out. Voilà! The transformation is revealed to the user.

This simple yet effective program swiftly flips the case of each character, showcasing the power of Java’s built-in methods.

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Output


Enter a string to convert: 
Hello World
Converted string: hELLO wORLD

Real-Life Uses of Case-Swapping in Java

Processing User Input: Consider a sign-up form where a user enters their name. Often, we want to display names consistently in reports or on webpages. For instance, if a user inputs their name as “john DOE,” applying a Java program to replace lower-case characters with upper-case and vice-versa ensures it’s displayed uniformly as “JOHN doe,” avoiding awkward capitalization issues.

Formatting Text Messages: Think about messaging apps that might need to transform text based on user preferences or to highlight certain words. Using a Java program that swaps lowercase letters with uppercase and vice versa, app developers can quickly change how they display messages, highlight important words, or create fun text effects.
Data Normalization in Databases: In databases, consistent data entry is crucial for effective queries. For instance, names and other text entries stored uniformly are easier to manage and search. By converting text to a standard format, such as swapping lower-case characters with upper-case using a Java program, databases remain tidy, promoting consistency across entries.
Improving Readability: To enhance readability or add stylistic flair, an eBook reader might adjust the font case. A Java program can replace lowercase characters with uppercase ones and vice versa, making the text more visually appealing and easier on the eyes for certain readers.

Common Interview Questions on Java Case Conversion

What is the primary function of the program?
The program swaps upper-case letters for lower-case ones and vice-versa in a string.
Which Java method can be used to change case?
Use the toLowerCase() and toUpperCase() methods from the Character class to swap lowercase and uppercase letters in a string efficiently

How do you handle non-alphabet characters?
Non-alphabet characters remain unchanged when the program executes.
Can this code work for accented characters?
Basic implementations usually ignore accented characters, but you can enhance them using libraries.
How does this program relate to string manipulation?
String manipulation is key as the program iterates through and modifies each character.

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Conclusion

In conclusion, creating a Java Program to replace lower-case characters with upper-case and vice-versa is a fantastic learning experience for beginners. By understanding string manipulation, loops, and conditionals, you grasp key Java concepts. This practice enhances your coding skills and boosts problem-solving abilities. Additionally, such programs have real-world applications in text handling and formatting. If you’re eager to deepen your knowledge, explore more at Newtum. Keep experimenting with Java, and share your creations with fellow learners. Your coding journey is just beginning—embrace it with enthusiasm and creativity!

Edited and Compiled by

This blog was compiled an edited by Rasika Deshpande, who has over 4 years of experience in content creation. She’s passionate about helping beginners understand technical topics in a more interactive way.