Class NullnessUtils

  extended by checkers.nullness.NullnessUtils

public final class NullnessUtils
extends Object

Utilities class for the Nullness Checker.

To avoid the need to write the NullnessUtils class name, do:

import static checkers.nullness.NullnessUtils.castNonNull;

Runtime Dependency

Please note that using this class introduces a Runtime dependency. This means that if you need to distribute (or link to) the Checker Framework, along with your binaries. To eliminate this dependency, you can simply copy this class into your own project.

Method Summary
Modifier and Type Method and Description
<T extends @Nullable Object>
castNonNull(T ref)
          A method that suppresses warnings from the Nullness Checker.
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail


public static <T extends @Nullable Object> T castNonNull(T ref)
A method that suppresses warnings from the Nullness Checker.

The method takes a possibly-null reference, unsafely casts it to have the @NonNull type qualifier, and returns it. The Nullness Checker considers both the return value, and also the argument, to be non-null after the method call. Therefore, the castNonNull method can be used either as a cast expression or as a statement. The Nullness Checker issues no warnings in any of the following code:

   // one way to use as a cast:
   @NonNull String s = castNonNull(possiblyNull1);

   // another way to use as a cast:

   // one way to use as a statement:
The castNonNull method is intended to be used in situations where the programmer definitively knows that a given reference is not null, but the type system is unable to make this deduction. It is not intended for defensive programming, in which a programmer cannot prove that the value is not null but wishes to have an earlier indication if it is. See the Checker Framework manual for further discussion.

The method throws AssertionError if Java assertions are enabled and the argument is null. If the exception is ever thrown, then that indicates that the programmer misused the method by using it in a circumstance where its argument can be null.

ref - a possibly-null reference
the argument, casted to have the type qualifier @NonNull