I'd like to find redundant blocks of code in my service. Is there a way to check when that last time this code was used runtime? The service is running on GCP.
I don't think there's a great solution to your problem but you could instrument, perhaps via Aspect-Oriented Programming (AOP), selected places in your code with simple logging statements and then monitor those.
You should avoid including any "hot code" which is executed very frequently because you can slow down your service and produce an overwhelming amount of logs (harder to manage and costly).
There's a lot of way to do this, but personally, I would use logging into this function and then let this app running normally. Then, you'll just have to check you log files and check for your logging message occurrences.
However, I'm not sure if it is possible to get this information without any action of your part to see previous usages of your code block.
I am having a fairly large legacy (swing) application and currently brainstorming and evaluating the strategies to add logging in it.
Key point is that it's fairly large (like I said above) and thinking what could be the strategy to do it quickly and completely (100% coverage for argument sake) (let's say logging is no customer facing core business functionality, so let's say not getting paid for it)
So the two strategies as such are -
Do use log4j2 add the debug statements, add appenders, file rolling rules, add dynamic on/off and change of log levels etc and thus do it the way it ideally should be done.
Use AOP to define endpoints and advices declaratively/programmaticly. Device such elaborate rules, add in the rest of the part (appenders, rolling rules etc.) and thus wont be touching each and every file and adding a revision just for that.
The second strategy is what I want to explore if someone has experience with, if somebody has gone that route.
The cons I can think of -
No standard / convention in apps, would be 99% impossible to define endpoints completely
Sphagetti and unmaintainable code in AOP module above, largely a result of the above problem
Adding same and matching set to logging to future classes.
Can you guys suggest me wither ways
While I am a big proponent of refactoring and clean code, I suggest you use AspectJ to add logging and see how far you get. Probably you will be surprised by how much logging you get with a little aspect.
IMHO logging is a cross-cutting concern and not core functionality. I would try to avoid logging in my core code. My expecience with AspectJ is only positive, I warmly recommend it. You should take some time to get acquainted with its power, though.
If you need something like a call trace (maybe neatly indented) or just plain method call logging with parameters and maybe return values, you will get quick results with AspectJ without cluttering your application code. The aspect can always be improved and maintained in a single spot, which is very clean. No need to be afraid of spaghetti aspect code. It will not happen if you don't totally abuse AspectJ.
You will only run into problems if your core code is already spaghetti code and you have very long methods which need log statements inside those methods and not around them. Then you might need to refactor and break down monster methods into smaller ones. But that is a problem no matter which logging approach you choose. My own experience with ugly legacy code and AspectJ-based logging tells me that it helps a lot because even spaghetti code calls other methods and that can be nicely traced in AspectJ.
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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.
Are there any tools out there that I could use to help me in analyzing call hierarchies of Java code? I am essentially looking for a way to select a method, generate the hierarchy, and then serialize to disk the highest level pieces of the hierarchy paths (all the roots) so that I can get some stats on it and get a better idea of risk/testing effort if this code were to be refactored.
My end goal is for any given method in a Java web app (no matter what layer it's in), figure out all the entry points into the application (Struts actions, web services) that a given method is utilized by. Eclipse has a nice tool that I use all the time for call hierarchies, but the method I'm analyzing is so heavily utilized that it won't be practical for me to go through manually expanding the trees and typing everything by hand.
Any help would be greatly appreciated.
Take a look at Cobertura. It's a tool to monitor test coverage but there's no reason it can't be used for what you need. The reports (sample report) are very comprehensive, allowing you to drill down to see which lines were executed and now many times.
A similar tool is Emma, which has been updated more recently than Cobertura. I've never used Emma so I can't comment on how well it works. The sample report looks similar to Cobertura's.