Cognizant Interview Question

What is Lambda expression? Where we use the lambda? sample example? Method references in Java 8? Four type of method references? What is functional interface? what are the rules for defining the functional interface? Creating own functional interface? example for predefined functional interface? How to use the predefined functional interface? Interface changes in Java 8- why added default and static method in interface? Java 8 Abstract classes vs interfaces? Java 8 Stream tutorial? Java 8 stream filter? example for stream collectors class? Java for each example? StringJoiner example Optional class purpose? optional map vs optional flatmap Arrays parallelsort?