org.checkerframework.checker.nullness

Class NullnessUtil

java.lang.Object

org.checkerframework.checker.nullness.NullnessUtil

public final class NullnessUtil
extends Object

Utility class for the Nullness Checker.

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

import static org.checkerframework.checker.nullness.NullnessUtil.castNonNull;

or

import static org.checkerframework.checker.nullness.NullnessUtil.*;

Runtime Dependency

Please note that using this class introduces a runtime dependency. This means that 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
static <T> T	castNonNull(T ref) A method that suppresses warnings from the Nullness Checker.
static <T> T[]	castNonNullDeep(T[] arr) Like castNonNull, but whereas that method only checks and casts the reference itself, this traverses all levels of the argument array.
static <T> T[][]	castNonNullDeep(T[][] arr) Like castNonNull, but whereas that method only checks and casts the reference itself, this traverses all levels of the argument array.
static <T> T[][][]	castNonNullDeep(T[][][] arr) Like castNonNull, but whereas that method only checks and casts the reference itself, this traverses all levels of the argument array.
static <T> T[][][][]	castNonNullDeep(T[][][][] arr) Like castNonNull, but whereas that method only checks and casts the reference itself, this traverses all levels of the argument array.
static <T> T[][][][][]	castNonNullDeep(T[][][][][] arr) Like castNonNull, but whereas that method only checks and casts the reference itself, this traverses all levels of the argument array.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

castNonNull

@EnsuresNonNull(value="#1")
public static <T> 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:
   castNonNull(possiblyNull2).toString();

   // one way to use as a statement:
   castNonNull(possiblyNull3);
   possiblyNull3.toString();`
 

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.

Parameters:

ref - a reference of @Nullable type

Returns:

the argument, casted to have the type qualifier @NonNull

castNonNullDeep

@EnsuresNonNull(value="#1")
public static <T> T[] castNonNullDeep(T[] arr)

Like castNonNull, but whereas that method only checks and casts the reference itself, this traverses all levels of the argument array. The array is recursively checked to ensure that all elements at every array level are non-null.

See Also:

castNonNull(Object)

castNonNullDeep

@EnsuresNonNull(value="#1")
public static <T> T[][] castNonNullDeep(T[][] arr)

Like castNonNull, but whereas that method only checks and casts the reference itself, this traverses all levels of the argument array. The array is recursively checked to ensure that all elements at every array level are non-null.

See Also:

castNonNull(Object)

castNonNullDeep

@EnsuresNonNull(value="#1")
public static <T> T[][][] castNonNullDeep(T[][][] arr)

Like castNonNull, but whereas that method only checks and casts the reference itself, this traverses all levels of the argument array. The array is recursively checked to ensure that all elements at every array level are non-null.

See Also:

castNonNull(Object)

castNonNullDeep

@EnsuresNonNull(value="#1")
public static <T> T[][][][] castNonNullDeep(T[][][][] arr)

Like castNonNull, but whereas that method only checks and casts the reference itself, this traverses all levels of the argument array. The array is recursively checked to ensure that all elements at every array level are non-null.

See Also:

castNonNull(Object)

castNonNullDeep

@EnsuresNonNull(value="#1")
public static <T> T[][][][][] castNonNullDeep(T[][][][][] arr)

Like castNonNull, but whereas that method only checks and casts the reference itself, this traverses all levels of the argument array. The array is recursively checked to ensure that all elements at every array level are non-null.

See Also:

castNonNull(Object)