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Findbugs

Findbugs. Tin Bui-Huy September, 2009. Content. What is bug? What is Findbugs? How to use Findbugs? Other static analysis tools for Java. What is bug?. An error or defect in software or hardware that causes a program to malfunction. Bug fixing cost. What is Findbugs?.

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Findbugs

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  1. Findbugs Tin Bui-Huy September, 2009

  2. Content • What is bug? • What is Findbugs? • How to use Findbugs? • Other static analysis tools for Java

  3. What is bug? • An error or defect in software or hardware that causes a program to malfunction

  4. Bug fixing cost

  5. What is Findbugs? • Result of a research project at the University of Maryland • Static analysis tool for Java

  6. What is Findbugs? • Not concerned by formatting or coding standards • Concentrates on detecting potential bugs and performance issues • Can detect many types of common, hard-to-find bugs

  7. How it works? • Use “bug patterns” to detect potential bugs • Examples Address address = client.getAddress(); if ((address != null) || (address.getPostCode() != null)) { ... } NullPointerException public class ShoppingCart { private List items; public addItem(Item item) { items.add(item); } } Uninitialized field

  8. What Findbugs can do? • FindBugs comes with over 200 rules divided into different categories: • Correctness E.g. infinite recursive loop, reads a field that is never written • Bad practice E.g. code that drops exceptions or fails to close file • Performance • Multithreaded correctness • Dodgy • E.g. unused local variables or unchecked casts

  9. How to use Findbugs? • Standalone Swing application • Eclipse plug-in • Integrated into the build process (Ant or Maven)

  10. Steps to Run Findbugs Standalone • Finbugs’ GUI brought up • Select File | New project

  11. Steps to Run Findbugs Standalone • Select byte code files and their source code [Point to jar files or class files] [Point to java files]

  12. Steps to Run Findbugs Standalone • FindBugs’ results

  13. Selectively Suppressing Rules with FindBug Filters • Select Edit | Preferences then move to Filter • Add some filters that meet your expectation

  14. AT: Sequence of calls to concurrent abstraction may not be atomic DC: Possible double check of field DL: Synchronization on Boolean DL: Synchronization on boxed primitive DL: Synchronization on interned String DL: Synchronization on boxed primitive values Dm: Monitor wait() called on Condition Dm: A thread was created using the default empty run method ESync: Empty synchronized block IS: Inconsistent synchronization IS: Field not guarded against concurrent access JLM: Synchronization performed on Lock JLM: Synchronization performed on util.concurrent instance JLM: Using monitor style wait methods on util.concurrent abstraction LI: Incorrect lazy initialization of static field LI: Incorrect lazy initialization and update of static field ML: Synchronization on field in futile attempt to guard that field ML: Method synchronizes on an updated field MSF: Mutable servlet field MWN: Mismatched notify() MWN: Mismatched wait() NN: Naked notify NP: Synchronize and null check on the same field. No: Using notify() rather than notifyAll() RS: Class's readObject() method is synchronized

  15. RV: Return value of putIfAbsent ignored, value passed to putIfAbsent reused Ru: Invokes run on a thread (did you mean to start it instead?) SC: Constructor invokes Thread.start() SP: Method spins on field STCAL: Call to static Calendar STCAL: Call to static DateFormat STCAL: Static Calendar field STCAL: Static DateFormat SWL: Method calls Thread.sleep() with a lock held TLW: Wait with two locks held UG: Unsynchronized get method, synchronized set method UL: Method does not release lock on all paths UL: Method does not release lock on all exception paths UW: Unconditional wait VO: An increment to a volatile field isn't atomic VO: A volatile reference to an array doesn't treat the array elements as volatile WL: Synchronization on getClass rather than class literal WS: Class's writeObject() method is synchronized but nothing else is Wa: Condition.await() not in loop Wa: Wait not in loop

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