I would consider that we have a clear understating of Functional Interfaces from the Topic "The Functional Interfaces in Java 8". We have also covered other topics related to it like Why it is introduced, its benefits & when to use it. However, some commonly used Predefined Functional Interfaces are listed in the attached table. Moreover, we will discuss all of them in detail in below sections. What are Predefined Functional Interfaces? Benefits of Using them? Java 8 has provided some Predefined (Built-in) Functional Interfaces to make our programming easier. Moreover, Predefined Functional Interfaces include most commonly used methods which are available to a programmer by default. In our day to day programming many times we come across re-occurring functionalities to be