Java 8 Lambdas and Streams - Good practices

Java version 8/1.8 has become the industry standard and enables developers to use Lambda expressions, Stream API, functional interfaces due to their popularity, performance improvements etc.,
1. Java lambda expressions are Java's first step into functional programming. A Java lambda expression is thus a function which can be created without belonging to any class and can be passed around as if it was an object and executed on demand.
2. Stream API is used to process collections of objects. A stream is a sequence of objects that supports various methods which can be pipelined to produce the desired result.
3. A functional interface is an interface that contains only one abstract method. They can have only one functionality to exhibit.
The question is as a developer are we following good practices in applying these powerful features to our code? Following good practices will help in writing maintainable and easily understandable code, increases efficiency and reduces cost. In this session, I'll share some good practices for using Java 8/1.8 features.