I have already talked about 2 most important features added in Java 8 in my last posts, i.e. Lambda and Streams. Apart from these there were few interesting additions.

Method definition in interfaces: For long time, Java has avoided multiple inheritance due to dreaded diamond problem. They had given us interfaces which did not had method definition, which could have been implemented by a class in multiple numbers. Now, Java has relieved the restriction a bit by allowing static and default methods definition in interfaces.
What about multiple inheritance diamond problem? Well if compiler cannot decide which implementation to use it will thrown an exception.

ForEach: For Collections like Lists, instead of creating an explicit iterator one can use forEach.

Optional: There can be a situation when a method can return null, in such situations the value can be saved in optional class.

Good reads: https://www.journaldev.com/2389/java-8-features-with-examples
http://www.baeldung.com/java-8-new-features