Effective Java Item 44 - Where is the `DoubleToObjFunction` in the standard library?

Question

Background

In Effective Java at Item 44, the author recommended the use of standard functional interfaces (instead of defining custom ones). In relation to java.util.function package, the author:

• listed the six basic forms: UnaryOperator<T>, BinaryOperator<T>, Predicate<T>, Function<T, R>, Supplier<T>, Consumer<T>;

• explained that there are three variants to each of the six basic forms that operate on the primitive types, giving as examples IntPredicate, LongBinaryOperator, and LongFunction<int[]>;

• and in the next paragraph mentioned the following:

  There are nine additional variants of the Function interface... If the source is a primitive and the result is an object reference, prefix Function with SrcToObj, for example DoubleToObjFunction (three variants).

Question

Where is this DoubleToObjFunction referred to by the author?

Notice in the third bullet point above that he used the words "nine additional variants", and hence could not have been referring the DoubleFunction since that would be the covered in the second bullet point.

I have tried a basic Google search of the function name in quotation, and also looked at the latest Java documentation on java.util.function but couldn't seem to find anything.

Answer 1

There are no interfaces called DoubleToObjFunction,LongToObjFunction and IntToObjFunction in Java 8,but interfaces called ToDoubleFunction,ToLongFunction and ToIntFunction which are not mentioned by the author in item 44. It maybe a errata.