org.apache.calcite.linq4j

Class Nullness

java.lang.Object

org.apache.calcite.linq4j.Nullness

public class Nullness
extends Object

The methods in this class allow to cast nullable reference to a non-nullable one. This is an internal class, and it is not meant to be used as a public API.

The class enables to remove checker-qual runtime dependency, and helps IDEs to see the resulting types of castNonNull better.

Method Summary

Modifier and Type	Method and Description
static <T> T	castNonNull(T ref) Allows you to treat a nullable type as non-nullable with no assertions.
static <T> T[]	castNonNullArray(T[] ts) Allows you to treat an array of nullable values as an array of non-nullable values.
static <T> List<T>	castNonNullList(List<? extends T> ts) Allows you to treat a list of nullable values as an list of non-nullable values.
static <T> T	castToInitialized(T ref) Allows you to treat an uninitialized or under-initialization object as initialized with no assertions.

Methods inherited from class java.lang.Object

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

Method Detail

castNonNull

@Pure
 @EnsuresNonNull(value="#1")
public static <T> T castNonNull(T ref)

Allows you to treat a nullable type as non-nullable with no assertions.

It is useful in the case you have a nullable lately-initialized field like the following:

 class Wrapper<T> {
   @Nullable T value;
 }
 

That signature allows you to use Wrapper with both nullable or non-nullable types: Wrapper<@Nullable Integer> vs Wrapper<Integer>. Suppose you need to implement

 T get() { return value; }
 

The issue is checkerframework does not permit that because T has unknown nullability, so the following needs to be used:

 T get() { return sneakyNull(value); }
 

Type Parameters:

T - the type of the reference

Parameters:

ref - a reference of @Nullable type, that is non-null at run time

Returns:

the argument, cast to have the type qualifier @NonNull

castNonNullArray

@Pure
public static <T> T[] castNonNullArray(T[] ts)

Allows you to treat an array of nullable values as an array of non-nullable values.

Type Parameters:

T - Type of the array elements

Parameters:

ts - Array

Returns:

the argument, cast so that elements are @NonNull

castNonNullList

@Pure
public static <T> List<T> castNonNullList(List<? extends T> ts)

Allows you to treat a list of nullable values as an list of non-nullable values.

Type Parameters:

T - Type of the list elements

Parameters:

ts - List

Returns:

the argument, cast so that elements are @NonNull

castToInitialized

@Pure
public static <T> T castToInitialized(T ref)

Allows you to treat an uninitialized or under-initialization object as initialized with no assertions.

Type Parameters:

T - The type of the reference

Parameters:

ref - A reference that was @Uninitialized at some point but is now fully initialized

Returns:

the argument, cast to have type qualifier @Initialized