1. StringBuilder
2. StringBuffer
3. java.nio.file.Files
4. Versioning
5. StringTokenizer
6. Programming languages
   1. Java
      1. Platforms
         1. SE (Standard Edition)
            1. Java Core
            2. Fundamentals
            3. Variables
            4. Class variables
            5. Local variables
            6. Methods
            7. Overriding methods
            8. Overloaded methods
            9. Constructors
            10. Data types
            11. By mutability
            12. Mutable
            13. Immutable
            14. By category
            15. Primitives
            16. Integer
            17. Floating-point
            18. Char
            19. Boolean
            20. Complex
            21. String
            22. Wrapper classes
            23. Operators
            24. Increment / decrement
            25. Relational
            26. Input / output
            27. Control Flow
            28. Block scope
            29. Conditional statements
            30. If
            31. Switch statement
            32. Ternary operator
            33. Loops
            34. For
            35. While
            36. Do-while
            37. For-each
            38. Type conversion
            39. Casting
            40. Upcasting
            41. Downcasting
            42. Arrays
            43. Multidimensional
            44. Classes
            45. Ordinary classes
            46. Abstract classes
            47. Inner classes
            48. Anonymous Inner Classes
            49. Enum classes
            50. Interfaces
            51. Iterable
            52. Iterator
            53. Comparator
            54. Comparable
            55. Marker Interfaces
            56. EventListener
            57. Cloneable
            58. Serializable
            59. Externalizable
            60. Generics
            61. By parameter type
            62. Any type
            63. Bounded type
            64. By category
            65. Generic classes
            66. Generic methods
            67. Exceptions
            68. Type
            69. Checked
            70. Custom
            71. Unchecked
            72. Handling
            73. Try-catch (try-catch-finally)
            74. Try-with-resources
            75. Throws
            76. Throw
            77. Packages
            78. JAR files
            79. Autoboxing
            80. Access Levels
            81. Package (default)
            82. Public
            83. Private
            84. Protected
            85. Keywords
            86. [access modifiers]
            87. static
            88. void
            89. final
            90. synchronized
            91. this
            92. super
            93. extends
            94. implements
            95. assert
            96. import
            97. transient
            98. I/O
            99. Bytes (file) I/O
            100. Character I/O
            101. java.util.Scanner
            102. Reader
            103. Writer
            104. Primitives I/O
            105. DataInputStream
            106. DataOutputStream
            107. Buffered I/O
            108. Buffered................
            109. Java Object I/O (serialize/deserialize)
            110. Network I/O
            111. URLConnection
            112. Database I/O
            113. Console I/O
            114. Concurrency
            115. Thread (class)
            116. Runnable (interface)
            117. Reflection
            118. Serialization
            119. RMI (remote method invocation)
            120. Annotation
            121. Lambda expressions
            122. Standard Java Packages
            123. Collections Framework
            124. Implementations
            125. Set
            126. HashSet
            127. TreeSet
            128. LindedHashSet
            129. List
            130. ArrayList
            131. LinkedList
            132. Queue
            133. Deque
            134. Map
            135. HashMap
            136. ConcurrentHashMap
            137. TreeMap
            138. LinkedHashMap
            139. Iteration mechanisms
            140. Iterator (interface)
            141. Iterable (interface)
            142. forEach (method)
            143. JDBC
            144. API documentation
            145. Javadoc
         2. EE (Enterprise Edition)
            1. Applets (deprecated)
            2. Servlets
            3. JSP
            4. JSF
            5. EJB
            6. JMS
      2. Third-party libraries
         1. Apache Commons
            1. Apache.commons.io.FileUtils
      3. JVM
         1. Garbage Collection
      4. Tools, Technologies, Frameworks
         1. Server
            1. Java Servlet Containers
            2. Apache Tomcat
            3. Java Application Servers
            4. Glassfish
            5. WildFly
         2. Testing
            1. JUnit
         3. ORM
            1. Hibernate
         4. Build Tools
            1. Maven
         5. Web Framework
            1. Spring MVC
         6. Code Analysis
            1. FindBugs
      5. IDE
         1. IDEA IntelliJ
      6. Core Features
         1. Abstraction
         2. Encapsulation
         3. Inheritance
         4. Polymorphism
   2. JavaScript
   3. HTML
   4. CSS
7. Algorithms and data structures
8. Patterns
9. Testing
10. Server Technologies
    1. Web servers
       1. Apache
       2. nginx
11. Version Control System
    1. Centralized
    2. Distributed
       1. Git
          1. Basic console commands
             1. git init
             2. git status
             3. git branch
             4. git branch xxx
             5. git checkout xxx
             6. git checkout -b xxx
             7. git add xxx
             8. git commit -m "xxx"
             9. git merge xxx
             10. git remote add origin xxx://xxxx/xxx.git
             11. git push -u origin master
             12. git pull origin master
          2. Git hosting
             1. github.com
             2. Basic repo operations
             3. Fork
             4. Clone
             5. Download as ZIP file
             6. Pull request
12. Databases
    1. Relational
       1. MySQL
    2. NoSQL
13. Unix
14. Networks
    1. Fundamentals
       1. Protocols
          1. TCP/IP
          2. UDP
          3. HTTP
          4. HTTPS
       2. Identifiers
          1. IP address
             1. IPv4
             2. IPv6
          2. Ports
          3. Sockets
             1. Socket address