Using toLowerCase() and toUpperCase() in Java

The method toLowerCase() converts all the characters in a string from uppercase to lowercase. The toUpperCase() method converts all the characters in a string from lowercase to uppercase. Nonalphabetical characters, such as digits, are unaffected. Here are the general forms of these methods:

String toLowerCase()
String toUpperCase()

Both methods return a String object that contains the uppercase or lowercase equivalent of the invoking String.

Here is an example that uses toLowerCase() and toUpperCase():

// Demonstrate toUpperCase() and toLowerCase().
class ChangeCase {
    public static void main(String args[]) {
        String s = "This is a test.";
        System.out.println("Original: " + s);
        String upper = s.toUpperCase();
        String lower = s.toLowerCase();
        System.out.println("Uppercase: " + upper);
        System.out.println("Lowercase: " + lower);
    }
}

The output produced by the program is shown here:

Original: This is a test.
Uppercase: THIS IS A TEST.
Lowercase: this is a test.