convertToUpperCase()

Step 1: Understand the Problem

The first step is to understand what we need to accomplish. Here, we want to write a Java function that transforms a string to uppercase. This implies transforming all lower-case letters in the string to upper-case.

Step 2: Java String Class

In Java, strings are objects that have various methods helpful in programming. The one that we are interested in is the toUpperCase() method. It converts all the characters in the string from lower-case to upper-case.

In Java, you'd do that as follows:

String str = "This is a sample string";
str = str.toUpperCase();

After execution str would contain "THIS IS A SAMPLE STRING".

Step 3: Write a Function to Transform a String to UpperCase

Let's create an toUpperCase() function which takes a string input and returns an uppercase string.

Here's the code:

public String toUpperCase(String str) { 
    return str.toUpperCase();
}

Step 4: Test the Function

It's always good practice to test your function to make sure it's working as expected. Here's how you could do it:

public static void main(String[] args) {
    System.out.println(toUpperCase("This is a sample string"));  // THIS IS A SAMPLE STRING
}

After running the main method, you should see the uppercase string printed in your console.

Step 5: Conclusion

In this exercise, we've created a simple function to convert a given string to uppercase using Java language built-in methods. We've also learnt how to call and test this function.

Here's the full code:

public class Main {

    public static void main(String[] args) {
        System.out.println(toUpperCase("This is a sample string"));  // THIS IS A SAMPLE STRING
    }

    public static String toUpperCase(String str) { 
        return str.toUpperCase();
    }
}