I am trying to create an index of unused Java methods in the form of a json file.
There are a couple different ways in which the methods can be referenced. I have already checked for all the other ways and have a relatively small list of possibly unused java methods.
The final way in which a method can be used is in other java files. They would be called with a basic class.method(args,args2,etc...) syntax somewhere in the java source code.
My question is, is there an easy way to just check my list of possible unused methods to see if any of them are not used in the java code. It would be ideal if this could be done at runtime, but it would also work if I could create a file that I could then read in at runtime.
I have tried using pre-built software like UCDetector, but the source code is huge, and running UCDetector takes hours and often doesn't even finish. It also checks all methods to see if they are used which is a waste of time since I have narrowed it down to a small number of possible methods to check.
You should use your IDE (eclipse, intelliJ), or some static code analysis tool such as findbugs, pmd, checkstyle.
It seems like you are trying to reinvent the wheel.
One option might be to use "coverage analysis" tools to see what is not used (https://en.m.wikipedia.org/wiki/Java_Code_Coverage_Tools). If you have good branch coverage with your unit tests, simply running the tests with coverage will yield the result you're looking for. If you don't have good tests coverage, you might run the application itself with code instrumented for coverage calculation, but as with unit tests - the quality of the result will depend on the amount of code executed with your unit tetst or manual test.
Some examples of the coverage tools you might use are : JaCoCo (http://www.eclemma.org/jacoco/) and Cobertura (http://cobertura.github.io/cobertura).
Alternatively you might instrument your code yourself in order to log methods usage, as it might be more lightweight than calculating full line coverage. This is however indeed reinventing the wheel.
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What tools do you use to find unused/dead code in large java projects? Our product has been in development for some years, and it is getting very hard to manually detect code that is no longer in use. We do however try to delete as much unused code as possible.
Suggestions for general strategies/techniques (other than specific tools) are also appreciated.
Edit: Note that we already use code coverage tools (Clover, IntelliJ), but these are of little help. Dead code still has unit tests, and shows up as covered. I guess an ideal tool would identify clusters of code which have very little other code depending on it, allowing for docues manual inspection.
An Eclipse plugin that works reasonably well is Unused Code Detector.
It processes an entire project, or a specific file and shows various unused/dead code methods, as well as suggesting visibility changes (i.e. a public method that could be protected or private).
CodePro was recently released by Google with the Eclipse project. It is free and highly effective. The plugin has a 'Find Dead Code' feature with one/many entry point(s). Works pretty well.
I would instrument the running system to keep logs of code usage, and then start inspecting code that is not used for months or years.
For example if you are interested in unused classes, all classes could be instrumented to log when instances are created. And then a small script could compare these logs against the complete list of classes to find unused classes.
Of course, if you go at the method level you should keep performance in mind. For example, the methods could only log their first use. I dont know how this is best done in Java. We have done this in Smalltalk, which is a dynamic language and thus allows for code modification at runtime. We instrument all methods with a logging call and uninstall the logging code after a method has been logged for the first time, thus after some time no more performance penalties occur. Maybe a similar thing can be done in Java with static boolean flags...
I'm suprised ProGuard hasn't been mentioned here. It's one of the most mature products around.
ProGuard is a free Java class file shrinker, optimizer, obfuscator,
and preverifier. It detects and removes unused classes, fields,
methods, and attributes. It optimizes bytecode and removes unused
instructions. It renames the remaining classes, fields, and methods
using short meaningless names. Finally, it preverifies the processed
code for Java 6 or for Java Micro Edition.
Some uses of ProGuard are:
Creating more compact code, for smaller code archives, faster transfer across networks, faster loading, and smaller memory
footprints.
Making programs and libraries harder to reverse-engineer.
Listing dead code, so it can be removed from the source code.
Retargeting and preverifying existing class files for Java 6 or higher, to take full advantage of their faster class loading.
Here example for list dead code: https://www.guardsquare.com/en/products/proguard/manual/examples#deadcode
One thing I've been known to do in Eclipse, on a single class, is change all of its methods to private and then see what complaints I get. For methods that are used, this will provoke errors, and I return them to the lowest access level I can. For methods that are unused, this will provoke warnings about unused methods, and those can then be deleted. And as a bonus, you often find some public methods that can and should be made private.
But it's very manual.
Use a test coverage tool to instrument your codebase, then run the application itself, not the tests.
Emma and Eclemma will give you nice reports of what percentage of what classes are run for any given run of the code.
We've started to use Find Bugs to help identify some of the funk in our codebase's target-rich environment for refactorings. I would also consider Structure 101 to identify spots in your codebase's architecture that are too complicated, so you know where the real swamps are.
In theory, you can't deterministically find unused code. Theres a mathematical proof of this (well, this is a special case of a more general theorem). If you're curious, look up the Halting Problem.
This can manifest itself in Java code in many ways:
Loading classes based on user input, config files, database entries, etc;
Loading external code;
Passing object trees to third party libraries;
etc.
That being said, I use IDEA IntelliJ as my IDE of choice and it has extensive analysis tools for findign dependencies between modules, unused methods, unused members, unused classes, etc. Its quite intelligent too like a private method that isn't called is tagged unused but a public method requires more extensive analysis.
In Eclipse Goto Windows > Preferences > Java > Compiler > Errors/Warnings
and change all of them to errors. Fix all the errors. This is the simplest way. The beauty is that this will allow you to clean up the code as you write.
Screenshot Eclipse Code :
IntelliJ has code analysis tools for detecting code which is unused. You should try making as many fields/methods/classes as non-public as possible and that will show up more unused methods/fields/classes
I would also try to locate duplicate code as a way of reducing code volume.
My last suggestion is try to find open source code which if used would make your code simpler.
The Structure101 slice perspective will give a list (and dependency graph) of any "orphans" or "orphan groups" of classes or packages that have no dependencies to or from the "main" cluster.
DCD is not a plugin for some IDE but can be run from ant or standalone. It looks like a static tool and it can do what PMD and FindBugs can't. I will try it.
P.S. As mentioned in a comment below, the Project lives now in GitHub.
There are tools which profile code and provide code coverage data. This lets you see (as code is run) how much of it is being called. You can get any of these tools to find out how much orphan code you have.
FindBugs is excellent for this sort of thing.
PMD (Project Mess Detector) is another tool that can be used.
However, neither can find public static methods that are unused in a workspace. If anyone knows of such a tool then please let me know.
User coverage tools, such as EMMA. But it's not static tool (i.e. it requires to actually run the application through regression testing, and through all possible error cases, which is, well, impossible :) )
Still, EMMA is very useful.
Code coverage tools, such as Emma, Cobertura, and Clover, will instrument your code and record which parts of it gets invoked by running a suite of tests. This is very useful, and should be an integral part of your development process. It will help you identify how well your test suite covers your code.
However, this is not the same as identifying real dead code. It only identifies code that is covered (or not covered) by tests. This can give you false positives (if your tests do not cover all scenarios) as well as false negatives (if your tests access code that is actually never used in a real world scenario).
I imagine the best way to really identify dead code would be to instrument your code with a coverage tool in a live running environment and to analyse code coverage over an extended period of time.
If you are runnning in a load balanced redundant environment (and if not, why not?) then I suppose it would make sense to only instrument one instance of your application and to configure your load balancer such that a random, but small, portion of your users run on your instrumented instance. If you do this over an extended period of time (to make sure that you have covered all real world usage scenarios - such seasonal variations), you should be able to see exactly which areas of your code are accessed under real world usage and which parts are really never accessed and hence dead code.
I have never personally seen this done, and do not know how the aforementioned tools can be used to instrument and analyse code that is not being invoked through a test suite - but I am sure they can be.
There is a Java project - Dead Code Detector (DCD). For source code it doesn't seem to work well, but for .jar file - it's really good. Plus you can filter by class and by method.
Netbeans here is a plugin for Netbeans dead code detector.
It would be better if it could link to and highlight the unused code. You can vote and comment here: Bug 181458 - Find unused public classes, methods, fields
Eclipse can show/highlight code that can't be reached. JUnit can show you code coverage, but you'd need some tests and have to decide if the relevant test is missing or the code is really unused.
I found Clover coverage tool which instruments code and highlights the code that is used and that is unused. Unlike Google CodePro Analytics, it also works for WebApplications (as per my experience and I may be incorrect about Google CodePro).
The only drawback that I noticed is that it does not takes Java interfaces into account.
I use Doxygen to develop a method call map to locate methods that are never called. On the graph you will find islands of method clusters without callers. This doesn't work for libraries since you need always start from some main entry point.
I am wondering if there is a tool that can identify cohesive blocks of code within JAVA source code.
For example if I had a long method that I would like to extract another method from - is there any tool that automatically can tell me large chunks of code that would be worth extracting?
There are plug-ins like PMD (for eclipse) & FindBugs etc., to do static code review which flags code based on rules your configured.
Google CodePro Analytics has an Eclipse plug-in that can provide a bunch of statistics like lines of code and cyclomatic complexity that can be good indicators that a method should be refactored.
I don't think you will find a tool that can automatically refactor 'cohesive' blocks of code into methods. There is too much subjectivity in that.
I looked for a similar tool with another question: https://stackoverflow.com/questions/12016289/tool-for-visualizing-dependencies-inside-a-java-class just on a slightly higher level: a single class.
I think the same answer applies: There isn't anything like that. There are tools though that provide information from which you might extract the information you are looking for.
I'd look into DependencyFinder. It provides access to all the bits and pieces of the code, so you could find clusters of code elements that access a common set of variables. Unfortunately I found the API a little confusing and not well documented, so you'll need some try and error or get into contact with the author. It also probably won't give you access to whitespace I think. But I don't think this is a valid approach anyway.
Another Tool you might want to look into is JaMoPP It should even have information about whitespace. Although it is a Java Plugin you can use the underlying library independent of eclipse (I think).
Check out Sonar It has very good support for finding duplicate code blocks.
Sonar uses PMD and FindBugs underlying. It also generates some custom metrics like class complexity, method complexity which points to classes / methods that are too large and which are candidate for breaking down.
Control blocks (i.e. conditionals and loops) are "cohesive" in that you cannot readily extract blocks of code that cross control block boundaries. Find blocks that can be replaced by a method call, that makes the original method easier to understand. You will have the best impact on complexity by extracting out the regions of deepest control flow nesting, so this is a good place to start. You don't need a tool as such - the code itself has the info you need.
Developers who have used eclipse cannot miss out the Cntrl+Shift+G combo - the easiest way to find all references to a particular member/method/class in your workspace.
Consider a scenario where you are a new guy maintaining a web application written in java. Now, you are about to change a method signature, and you do a Cntl+Shift+G to find all references to the said method (yes, hoping that you are not doing depedency injection / reflection etc). However, a new guy, would want not to screw up any functionality in the application. How would ensure that the functional dependencies are not affected?
I guess..the question is a bit unclear.. lemme rephrase... Say you are changing something functional (an if loop in a business rule or whateva) - this will definetly CHANGE something else in the context of the application.. and at this point you wish there was something (a plugin?) in eclipse, that would tell you - "hey noob..don't change this - it would affect this..." - Now, if you were to create something that does this for eclipse (plugin?) - where would you start? (tagging parts of scr code and introducing a depdency tree? etc?)
Perhaps I failed to understand your question, but I think I might have an answer. Take a look at nWire for Java (or PHP). It is a plugin for code exploration. Focusing on a piece of code, the developer can quickly determine where the method is invoked, where the class is used, etc. This makes it easier to understand what you are about to change.
I am the developer of this plugin. If it is not exactly what you are looking for, let me know, I'll be happy to better understand what you are looking for.
Besides: ALT+SHIFT+C is the way to change a method signature. ALT+SHIFT+G "only" finds references, which is helpful of course.
vickirk mentionend the most important aspect here: Without having tests and a good code coverage you aren't able to apply any changes without risking a failing system afterwards.
The book "Working Effectively with Legacy Code" from Robert C Martin explains it nicely: All code, which is not covered by tests, is legacy code. You could draw the conclusion, that before you apply any functional change you need to ensure a sufficient test coverage.
Tagging parts in the source code seems like a bad idea, since these tags need to be additionally maintained, which usually never really happens in projects. :)
What about JDepend?
I'm trying to write rules for detecting some errors in annotated multi-threaded java programs. As a toy example, I'd like to detect if any method annotated with #ThreadSafe calls a method without such an annotation, without synchronization. I'm looking for a tool that would allow me to write such a test.
I've looked at source analyzers, like CheckStyle and PMD, and they don't really have cross-class analysis capabilities. Bytecode analysers, like FindBugs and JLint seem rather difficult to extend.
I'd settle for a solution to something even simpler, but posing the same difficulty: writing a custom rule that checks whether each overriden method is annotated with #Override.
Have you tried FindBugs? It actually supports a set of annotations for thread safety (the same as those used in Java Concurrency in Practice). Also, you can write your own custom rules. I'm not sure whether you can do cross-class analysis, but I believe so.
Peter Ventjeer has a concurrency checking tool (that uses ASM) to detect stuff like this. I'm not sure if he's released it publicly but he might able to help you.
And I believe Coverity's static/dynamic analysis tools for thread safety do checking like this.
You can do cross-class analysis in PMD (though I've never used it for this specific purpose). I think it's possible using this visitor pattern that they document, though I'll leave the specifics to you.
A simple tool to checkup on annotations is apt (http://java.sun.com/j2se/1.5.0/docs/guide/apt/ also part of Java 6 api in javax.annotation.processing) however this only has type information (ie I couldn't find a quick way to get at the inheritance hierarchy using the javax.lang.model api, however if you can load the class you can get that information using reflection).
Try javap + regexes (eg. Perl)