whats java lang nullpointer exeption?

Question

when i try to get into a spades room

Answer 1

public class NullPointerException
extends RuntimeException
Thrown when an application attempts to use null in a case where an object is required. These include:

Calling the instance method of a null object.
Accessing or modifying the field of a null object.
Taking the length of null as if it were an array.
Accessing or modifying the slots of null as if it were an array.
Throwing null as if it were a Throwable value.
Applications should throw instances of this class to indicate other illegal uses of the null object.


To summarize this is program bug.