Package 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
    Description
    static <T extends @Nullable Object>
    @NonNull T
    castNonNull(@Nullable T ref)
    Allows you to treat a nullable type as non-nullable with no assertions.
    static <T> @NonNull T[]
    castNonNullArray(@Nullable T[] ts)
    Allows you to treat an array of nullable values as an array of non-nullable values.
    static <T> List<@NonNull T>
    castNonNullList(List<? extends @Nullable T> ts)
    Allows you to treat a list of nullable values as an list of non-nullable values.
    static <T> T
    castToInitialized(@UnderInitialization 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 Details

    • castNonNull

      @Pure @EnsuresNonNull("#1") public static <T extends @Nullable Object> @NonNull T castNonNull(@Nullable 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 castNonNull(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> @NonNull T[] castNonNullArray(@Nullable 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<@NonNull T> castNonNullList(List<? extends @Nullable 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(@UnderInitialization 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