The main theme of Java 8 is support for functional programming. With increase in Database size and growth of multi-code CPU servers, there is need for Java to support such large-scale systems.
With new features of Java 8, it is possible to create functional programs to interact efficiently with Big Data systems. Support for Streams is very helpful in this regard.
Lambda expressions are very useful for cloud computing where we can pass code as data and run the same code on multiple servers.
Optional is a best practice that is borrowed from Google Guava library for handling the exceptional cases. This has made programs more robust with support for edge cases.Read the full book at www.amazon.com