@notnull

Marks an individual type, all types in a package or all types in a module as non-null.

Assigning null to an instance of a type marked as @nonnull is an error.

Passing null as a method argument of a type marked as @nonnull is an error.

@nullable

Marks an individual type, a field or a parameter as nullable.

Assigning null to a field of a type not marked as @nullable is a warning, except when the type itself has been marked with @nonnull, in which case it is an error.

Passing null as a method argument of a type not marked as @nullable is a warning, except when the type itself has been marked with @nonnull, in which case it is an error.

@immutable

Marks all parameters a package or module as immutable.

Assigning a value to a parameter marked as @immutable is an error.

@mutable

Marks a parameter or local variable as mutable.

Assigning a value to a parameter or local variable is a warning, except when the parameter is marked as @immutable, in which case it is an error.