Uses of Interface
java.util.function.ToDoubleFunction

Packages that use ToDoubleFunction 
Package Description
java.util
Contains the collections framework, some internationalization support classes, a service loader, properties, random number generation, string parsing and scanning classes, base64 encoding and decoding, a bit array, and several miscellaneous utility classes.
java.util.concurrent
Utility classes commonly useful in concurrent programming.
java.util.stream
Classes to support functional-style operations on streams of elements, such as map-reduce transformations on collections.