This is the best app to learn java in depth.We divided this app into four parts
1)Tutorial
2)Programs
3)Java 8 features
4)Rejax Expressions

Tutorial include:-
1)Fundamentals of OOP
2)Introduction to Java
3)Programming concept of basic java
4)Java Classes
5)Inheritance
6)Package and Interface
7)Exception Handling
8)Input Output
9)Multithreading
10)AWT
11)Swing
12)Applet
13)Collection freamwork

Java 8 features include:-
1)Lambda Expression
2)Functional Interface
3)Default mathods
4)Predicates etc.