Null pointer
A VALUE INDICATING THAT A POINTER DOES NOT REFER TO A VALID OBJECT
Null reference; NullPointerException; NULL pointer; Java.lang.NullPointerException; Null pointer exception; Billion-dollar mistake; Null pointer error
In computing, a null pointer or null reference is a value saved for indicating that the pointer or reference does not refer to a valid object. Programs routinely use null pointers to represent conditions such as the end of a list of unknown length or the failure to perform some action; this use of null pointers can be compared to nullable types and to the Nothing value in an option type.