A NullPointerException should indicate that a null value was unexpectedly encountered. Good programming practice dictates that code is structured to avoid NPE's. Explicitly throwing NullPointerException forces a method's callers to explicitly catch it, rather than coding to avoid it. Further, it makes it difficult to distinguish between the unexpectedly-encountered null value and the condition which causes the method to purposely throw an NPE. If an NPE is being thrown to indicate that a parameter to the method should not have been null, use the @NotNull annotation instead.

Noncompliant Code Sample

public void doSomething (String aString) throws NullPointerException 
{}

Compliant Solution

public void doSomething (@NotNull String aString)
{}