NullA null pointer exception is thrown when an application attempts to use null in a case where an object is required. These include:
- Calling the instance method of a
nullobject. - Accessing or modifying the field of a
nullobject. - Taking the length of
nullas if it were an array. - Accessing or modifying the slots of
nullas if it were an array. - Throwing
nullas if it were a Throwable value.
Applications should throw instances of this class to indicate other illegal uses of the null object.
Reference : http://docs.oracle.com/javase/8/docs/api/java/lang/NullPointerException.html