What is a null reference?

null reference is a special value that indicates the absence of an object instance. Essentially, it is an "empty" reference that does not point to any address in memory.

Key aspects:

• It is not an object by itself.
• Attempting to access members (fields or methods) through a null reference will result in an exception (for example, NullPointerException in Java or NullReferenceException in C#).
• It is used to indicate that a variable or field has not been initialized with an object.

Example in Java:

// Declaring a variable but not yet initialized with an object
String str = null;

// Attempting to call a method on a null reference will lead to NullPointerException
// int length = str.length();