Which method returns true if the string length is 0 in Java?

• A. isBlank()
• B. isEmpty()
• C. isNull()
• D. isWhitespace()

Answer: (B)

The method that returns true if the string length is 0 in Java is indeed the isEmpty() method. This method is part of the String class and specifically checks whether the string is empty, meaning it has a length of 0. When you call str.isEmpty() on a string object, it will return true if the string contains no characters.

This is useful for validating input or checking for empty strings in various contexts, such as user input validation or when processing data strings in an application. The isEmpty() method directly addresses the need to determine if a string is devoid of characters, making it straightforward and specific to this purpose.

In contrast, while isBlank() checks if a string is empty or only contains whitespace, it does not return true for strings that are entirely empty. The isNull() method is not relevant in this context as it checks for the reference of the object itself, not the content of the string. isWhitespace(), on the other hand, is used to determine if a specified character is a whitespace character, which does not apply to checking the length of a string. Thus, isEmpty() is the precise method for this requirement.