A <code>NullPointerException</code> should indicate that a <code>null</code> value was unexpectedly encountered. Good programming practice dictates that code is structured to avoid NPE's. 

Explicitly throwing <code>NullPointerException</code> 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 <code>null</code> 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 <code>@NotNull</code> annotation instead.

<h2>Noncompliant Code Sample</h2>
<pre>
public void doSomething (String aString) throws NullPointerException 
{}
</pre>

<h2>Compliant Solution</h2>
<pre>
public void doSomething (@NotNull String aString)
{}
</pre>