1. java tools
   1. java
   2. javaw
   3. javac
2. Java API
   1. java.lang
   2. java.io
   3. java.util
3. Java Virtual Machine
4. Java Language
   1. OOP
      1. Object
         1. States
            1. store in file
            2. Serializable
            3. store in memory
            4. Data
            5. Type
            6. primitive
            7. int
            8. byte
            9. short
            10. long
            11. char
            12. float
            13. double
            14. object refercence
            15. array
            16. []
            17. class
            18. interface
         2. Behaviors
            1. do ordered
            2. do together
            3. Multi-threading
            4. syncronized
      2. Encapsulation
         1. component
            1. Package
            2. Class
            3. containment
            4. fields
            5. member fields
            6. this
            7. getter
            8. setter
            9. static fields
            10. static
            11. constants
            12. static final
            13. constructors
            14. defaut constructor
            15. constructor with parameters
            16. methods
            17. contain statements
            18. expressions
            19. operators
            20. +,-,*,/,++,--
            21. >,<,==,>=,<=,!=
            22. &&,||,!
            23. &,|,^
            24. >>,<<
            25. =,+=,-=,&=,|=,*=,/=
            26. operands
            27. if
            28. if..else
            29. if...else if...else
            30. switch
            31. case
            32. break
            33. default
            34. while
            35. condition
            36. do
            37. do
            38. while
            39. condition
            40. break
            41. continue
            42. return
            43. try
            44. catch
            45. finalize
            46. throw
            47. Exception
            48. throws
            49. Nested Class
            50. Inner Class
            51. Member Class
            52. Local Class
            53. Anonymous Class
            54. Static Nested Class
            55. Scope
            56. Access Modifiers
            57. public
            58. protected
            59. (no modifier)
            60. private
      3. Inheritance
         1. Single Inheritance
            1. SubClass
            2. extends
            3. SuperClass
         2. Multiple Inheritance
            1. implements
            2. interface
      4. Abstraction
         1. abstract
      5. Polymorphism
   2. Flatform-independent
   3. Secure
   4. Robust
   5. Distributed
   6. Multi-Threaded