Nullable is a type annotation that makes no commitments about whether the value is null. Equivalently, the type includes the null value.

The Nullness Checker issues an error if null is assigned an expression of NonNull type.

Programmers typically write @Nullable to indicate that the value is not known to be NonNull. However, since @Nullable is a supertype of @NonNull, an expression that never evaluates to null can have a declared type of @Nullable.