Mastering Java: The Ultimate Quiz for 'Thinking in Java'

What method produces a new String object with all letters changed to lowercase?

1. tolowerCase()

2. toLowerCase()

3. lower()

4. convertToLower()

The correct answer is: toLowerCase()

The method toLowerCase() is the only built-in method in Java that changes all letters in a String to lowercase. Option A, tolowerCase(), is incorrect because it includes a typo and is not a valid method name. Option C, lower(), is incorrect because it is not a built-in method in Java. Option D, convertToLower(), is incorrect because it is not a valid method name in Java and there is no built-in method with this name. Therefore, the correct answer is B, toLowerCase().