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Code reviews


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Code reviews

  1. 1. Every Programmer Should Know Code Reviews Roger Xia July 2012
  2. 2. $ whoami• Programmer
  3. 3. Programming & Code review• Programming is – Taking an algorithm – Choosing a language – Using that language to implement algorithm and solve problems• Code review is –?
  4. 4. Why?• Increase Quality & Reduce Defects• Improve readability• Share knowledge in team• Know your workmate better!• Two Wrongs Can Make a Right• NOT personal attack!• NOT architect reviews everything
  5. 5. methodology• Team review (Planned 1-2 hour/week, Clear roles)• Pair programming (Share knowledge, 1 task)• Walkthrough (Author leads, reviewers take notes, higher level)• Peer review (Asynchronous)• Gerrit• Reaction & Ask questions
  6. 6. Preparation• Code Conventions• Findbugs• Tested• Test case
  7. 7. Take care of• naming convention spelling mistakes• business logic• refactoring• performance• security (attack, thread safe)
  8. 8. Refactoring• Refactoring modifies software to improve its readability, maintainability, and extensibility without changing what it actually does.• Martin Fowler uses “code smells” to identify when to refactor.• Boss: "Refactoring is an overhead activity - Im paid to write new, revenue generating features."
  9. 9. Code smells• Bad names• Duplicate code• Long method• Large class• Long parameter list• Temporary field• Speculative Generality• Data Class• Don’t flood log
  10. 10. Use Meaningful Names
  11. 11. Meaningful Names• Class names – Should be nouns or noun phrases. – Examples: Car, Account, DataRetrievalService, AddressParser• Method names – Should be verb or verbPhrases – Examples: parseData, deletePage, save – Methods that return boolean values should sound like question. – Examples: isAuthenticated, hasNoErrors, isEmpty• Interface and Implementation – ICache  LRUCache – IExport  ExportService• Constants – MAX_VALUE – SEP_COMMA, SEP_SEMICOLON
  12. 12. The Art of Readable code• The book!• I want to point out: – Use blank to separate logic block.
  13. 13. Comments for complexprocess, algorithm, reasons
  14. 14. Aiming for simplicity• Do one thing in a function (simple responsibility)• Have no side effects.• Prefer exceptions to return codes.• Format your code.
  15. 15. DRY -- Don’t repeat yourself• Duplicated code should be avoided.• Object Orientation, Abstract!• Design pattern!
  16. 16. OO Principles• Simple responsibility principle: Class should have one and only one reason to change.• Encapsulation: Modules should not know internal details of objects it manipulates.• Polymorphism -- Liskov’s substitution principle: A subclass can be used as an argument where a base class is expected.• Open-closed principle: Class should be open for extention, but closed for modification.
  17. 17. Design Patterns
  18. 18. Pay Attention to Performance• JAVA: JVM usage – Don’t create object in loop – Use ArrayList, HashMap etc as opposed to Vector, Hashtable etc (synchronized) where possible. Even better is to use just arrays where possible. – Set initial capacity of a collection (e.g. ArrayList, HashMap) and StringBuffer/StringBuilder appropriately. – Concurrent Collection, Lock – Lazy load or multi-threading where applicable. – Cache (LRUCache, Distributed Cache)
  19. 19. Pay Attention to Performance
  20. 20. Pay Attention to Security• Sandbox (security manager, access manager, Classloaders, policies)• Scope: Access modifier to help protect your classes, methods, fields. – public, protected, private, package – Exceptions: object serialization, reflection,• Immutable class – final – String – Insecure direct object reference of mutable object• Type safe – Casting• Thread safe• OOM (static), file description handler, release resources (File, DBConnection)• SQL injection• Single point of failure
  21. 21. • secure code
  22. 22. Have Fun and win