1. features
1.1. Object Oriented. language
1.2. Simple
1.3. Secured
1.4. Platform Independent.
1.5. Robust
1.6. Portable
1.7. Architecture neutral
1.8. Dynamic
1.9. Interpreted
1.10. High Performance
1.11. Multithreaded
1.12. Distributed
2. Application
2.1. Mobile Applications
2.2. Desktop GUI Applications
2.3. Web-based Applications
2.4. Web Servers and Application Servers
2.5. Enterprise Applications
2.6. Scientific Applications
2.7. Gaming Applications
2.8. Big Data Technologies
2.9. Business Applications
2.10. Distributed Applications
2.11. Cloud-based Applications
2.12. embedded system
3. JVM
4. Data types
4.1. primitive
4.1.1. Boolean
4.1.1.1. boolean
4.1.2. Numeric
4.1.2.1. charater
4.1.2.1.1. char
4.1.2.2. integeral
4.1.2.2.1. integer
4.1.2.2.2. floating-point
4.2. non primitive
4.2.1. Array
4.2.2. string
4.2.3. etc..
5. common libraries
5.1. Logging Libraries
5.2. JSON Parsing libraries
5.3. Unit Testing Libraries
5.4. General Purpose Libraries
5.5. HTTP Libraries
5.6. XML Parsing Libraries
5.7. Excel Reading Libraries
5.8. Bytecode Libraries
5.9. Database Connection Pool Libraries
5.10. Messaging Libraries
5.11. PDF Libraries
5.12. Date and Time Libraries
5.13. Collection Libraries
5.14. Email APIs
5.15. HTML Parsing Libraries
5.16. Cryptographic Library
5.17. Embedded SQL Database Library
5.18. JDBC Troubleshooting Libraries
5.19. Serialization Libraries
5.20. Networking Libraries
6. language basics
6.1. operators
6.1.1. Arithmetic
6.1.2. Relational
6.1.3. Bitwise
6.1.4. Logical
6.1.5. Assignment
6.1.6. Misc
6.2. Exception
6.2.1. try catch
6.2.2. try with resourses
6.2.3. finally block
6.2.4. throws
6.3. numbers and string
6.3.1. numbers
6.3.2. string
6.4. primltive types
7. oop (object oriented programming)
7.1. Object
7.1.1. common methods
7.1.1.1. Equals
7.1.1.2. Hashcode
7.1.1.3. toString
7.1.1.4. notify
7.1.1.5. wait
7.1.1.6. notifyall
7.2. Class
7.2.1. lambda Expression
7.2.2. Genarics
7.2.3. Enum
7.2.4. anonymous
7.2.5. nasted
7.2.6. static
7.2.7. final
7.2.8. package
7.3. Inheritance
7.3.1. interfaceses
7.3.2. Abstract classes
7.4. Polymorphism
7.4.1. over loading
7.4.2. overring
7.4.3. Runtime
7.4.4. static
7.4.5. casting
7.4.5.1. Downcasting
7.4.5.2. upcasting
7.5. Encapsulation
7.5.1. access modiiers
7.5.1.1. public
7.5.1.2. private
7.5.1.3. protected
7.5.1.4. package