What causes java lang IncompatibleClassChangeError

Question

I m packaging a Java library as a JAR  and it s throwing many java lang IncompatibleClassChangeErrors when I try to invoke methods from it  These errors seem to appear at random  What kinds of problems could be causing this error

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Adding my 2 cents  If you are using scala and sbt and scala-logging as dependency  then this can happen because scala-logging s earlier version had the name scala-logging-api So essentially the dependency resolutions do not happen because of different names leading to runtime errors while launching the scala application

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This means that you have made some incompatible binary changes to the library without recompiling the client code   Java Language Specification   13 details all such changes  most prominently  changing non-static non-private fields methods to be static or vice versa   Recompile the client code against the new library  and you should be good to go   UPDATE  If you publish a public library  you should avoid making incompatible binary changes as much as possible to preserve what s known as  binary backward compatibility    Updating dependency jars alone ideally shouldn t break the application or the build  If you do have to break binary backward compatibility  it s recommended to increase the major version number  e g  from 1 x y to 2 0 0  before releasing the change

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I ve faced this issue while undeploying and redeploying a war with glassfish  My class structure was like this   public interface A     public class AImpl implements A      and it was changed to   public abstract class A     public class AImpl extends A      After stopping and restarting the domain  it worked out fine   I was using glassfish 3 1 43

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An additional cause of this issue  is if you have Instant Run enabled for Android Studio   The fix  If you find you start getting this error  turn off Instant Run    Android Studio main settings Build  Execution  Deployment Instant Run Untick  Enable instant run       Why  Instant Run modifies a large number of things during development  to make it quicker to provide updates to your running App  Hence instant run  When it works  it is really useful  However  when an issue such as this strikes  the best thing to do is to turn off Instant Run until the next version of Android Studio releases

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In my case the error appeared when I  added the com nimbusds library in my application deployed on Websphere 8 5  The below exception occurred         Caused by  java lang IncompatibleClassChangeError  org objectweb asm AnnotationVisitor   The solution was to exclude the asm jar from the library      lt dependency gt       lt groupId gt com nimbusds lt  groupId gt       lt artifactId gt nimbus-jose-jwt lt  artifactId gt       lt version gt 5 1 lt  version gt       lt exclusions gt           lt exclusion gt               lt artifactId gt asm lt  artifactId gt               lt groupId gt org ow2 asm lt  groupId gt           lt  exclusion gt       lt  exclusions gt   lt  dependency gt

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I have a web application that deploys perfectly fine on my local machine s tomcat 8 0 20   However  when I put it into the qa environment  tomcat - 8 0 20   it kept on giving me the IncompatibleClassChangeError and it was complaining that I was extending on an interface  This interface was changed to an abstract class  And I compiled the parent and child classes and still I kept on getting the same issue  Finally  I wanted to debug  so  I changed the version on the parent to x 0 1-SNAPSHOT and then compiled everything and now it is working  If someone is still hitting the problem after following the answers given here  please make sure the versions in your pom xml are also correct  Change the versions to see if that works  If so  then fix the version problem

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Documenting another scenario after burning way too much time     Make sure you don t have a dependency jar that has a class with an EJB annotation on it   We had a common jar file that had an  local annotation   That class was later moved out of that common project and into our main ejb jar project  Our ejb jar and our common jar are both bundled within an ear   The version of our common jar dependency was not updated  Thus 2 classes trying to be something with incompatible changes

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I had the same issue  and later I figured out that I am running the application on Java version 1 4 while the application is compiled on version 6   Actually  the reason was of having a duplicate library  one is located within the classpath and the other one is included inside a jar file that is located within the classpath

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Please check if your code doesnt consist of two module projects that have the same classes names and packages definition  For example this could happen if someone uses copy-paste to create new implementation of interface based on previous implementation

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Your newly packaged library is not backward binary compatible  BC  with old version  For this reason some of the library clients that are not recompiled may throw the exception   This is a complete list of changes in Java library API that may cause clients built with an old version of the library to throw java lang IncompatibleClassChangeError if they run on a new one  i e  breaking BC     Non-final field become static  Non-constant field become non-static  Class become interface  Interface become class  if you add a new field to class interface  or add new super-class super-interface  then a static field from a super-interface of a client class C may hide an added field  with the same name  inherited from the super-class of C  very rare case     Note  There are many other exceptions caused by other incompatible changes  NoSuchFieldError  NoSuchMethodError  IllegalAccessError  InstantiationError  VerifyError  NoClassDefFoundError and AbstractMethodError   The better paper about BC is  Evolving Java-based APIs 2  Achieving API Binary Compatibility  written by Jim des Rivi  res   There are also some automatic tools to detect such changes    japi-compliance-checker clirr japitools sigtest japi-checker   Usage of japi-compliance-checker for your library   japi-compliance-checker OLD jar NEW jar   Usage of clirr tool   java -jar clirr-core-0 6-uber jar -o OLD jar -n NEW jar   Good luck

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All of the above - for whatever reason I was doing some big refactor and starting to get this   I renamed the package my interface was in and that cleared it  Hope that helps

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While these answers are all correct  resolving the problem is often more difficult   It s generally the result of two mildly different versions of the same dependency on the classpath  and is almost always caused by either a different superclass than was originally compiled against being on the classpath or some import of the transitive closure being different  but generally at class instantiation and constructor invocation    After successful class loading and ctor invocation  you ll get NoSuchMethodException or whatnot    If the behavior appears random  it s likely the result of a multithreaded program classloading different transitive dependencies based on what code got hit first    To resolve these  try launching the VM with -verbose as an argument  then look at the classes that were being loaded when the exception occurs   You should see some surprising information  For instance  having multiple copies of the same dependency and versions you never expected or would have accepted if you knew they were being included   Resolving duplicate jars with Maven is best done with a combination of the maven-dependency-plugin and maven-enforcer-plugin under Maven  or SBT s Dependency Graph Plugin  then adding those jars to a  section of your top-level POM or as imported dependency elements in SBT  to remove those dependencies     Good luck

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If this is a record of possible occurences of this error then   I just got this error on WAS  8 5 0 1   during the CXF  2 6 0  loading of the spring  3 1 1 release  configuration where a BeanInstantiationException rolled up a CXF ExtensionException  rolling up a IncompatibleClassChangeError  The following snippet shows the gist of the stack trace   Caused by  org springframework beans BeanInstantiationException  Could not instantiate bean class  org apache cxf bus spring SpringBus   Constructor threw exception  nested exception is org apache cxf bus extension ExtensionException             at org springframework beans BeanUtils instantiateClass BeanUtils java 162              at org springframework beans factory support SimpleInstantiationStrategy instantiate SimpleInstantiationStrategy java 76              at org springframework beans factory support AbstractAutowireCapableBeanFactory instantiateBean AbstractAutowireCapableBeanFactory java 990                  116 more Caused by  org apache cxf bus extension ExtensionException             at org apache cxf bus extension Extension tryClass Extension java 167              at org apache cxf bus extension Extension getClassObject Extension java 179              at org apache cxf bus extension ExtensionManagerImpl activateAllByType ExtensionManagerImpl java 138              at org apache cxf bus extension ExtensionManagerBus  lt init gt  ExtensionManagerBus java 131               etc                 at org springframework beans BeanUtils instantiateClass BeanUtils java 147                  118 more  Caused by  java lang IncompatibleClassChangeError   org apache neethi AssertionBuilderFactory             at java lang ClassLoader defineClassImpl Native Method              at java lang ClassLoader defineClass ClassLoader java 284               etc                 at com ibm ws classloader CompoundClassLoader loadClass CompoundClassLoader java 586              at java lang ClassLoader loadClass ClassLoader java 658              at org apache cxf bus extension Extension tryClass Extension java 163                  128 more   In this case  the solution was to change the classpath order of the module in my war file  That is  open up the war application in the WAS console under and select the client module s   In the module configuration  set the class-loading to be  parent last    This is found in the WAS console    Applicatoins -  Application Types -  WebSphere Enterprise Applications Click link representing your application  war  Click  Manage Modules  under  Modules  section Click link for the underlying module s  Change  Class loader order  to be   parent last

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For some reason the same exception is also thrown when using JNI and passing the jclass argument instead of the jobject when calling a Call Method     This is similar to the answer from Ogre Psalm33   void example JNIEnv  env  jobject inJavaList        jclass class List   env- gt FindClass  java util List         jmethodID method size   env- gt GetMethodID class List   size      I        long size   env- gt CallIntMethod class List  method size      should be passing  inJavaList  instead of  class List       std  cout  lt  lt   LIST SIZE    lt  lt  size  lt  lt  std  endl      I know it is a bit late to answer this question 5 years after being asked but this is one of the top hits when searching for java lang IncompatibleClassChangeError so I wanted to document this special case

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I have also discovered that  when using JNI  invoking a Java method from C    if you pass parameters to the invoked Java method in the wrong order  you will get this error when you attempt to use the parameters inside the called method  because they won t be the right type    I was initially taken aback that JNI does not do this checking for you as part of the class signature checking when you invoke the method  but I assume they don t do this kind of checking because you may be passing polymorphic parameters and they have to assume you know what you are doing   Example C   JNI Code   void invokeFooDoSomething         jobject javaFred   FredFactory  getFred       Get a Fred jobject     jobject javaFoo   FooFactory  getFoo       Get a Foo jobject     jobject javaBar   FooFactory  getBar       Get a Bar jobject     jmethodID methodID   getDoSomethingMethodId      Get the JNI Method ID       jniEnv- gt CallVoidMethod javaFoo                             methodID                             javaFred     Woops   I switched the Fred and Bar parameters                             javaBar            lt  lt  Insert error handling code here to discover the JNI Exception  gt  gt              This is where the IncompatibleClassChangeError will show up      Example Java Code   class Bar          class Fred       public int size               class Foo       public void doSomething Fred aFred  Bar anotherObject            if  name size    gt  0       Will throw a cryptic java lang IncompatibleClassChangeError                Do some stuff

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In my case  I ran into this error this way  pom xml of my project defined two dependencies A and B  And both A and B defined dependency on same artifact  call it C  but different versions of it  C 1 and C 2   When this happens  for each class in C maven can only select one version of the class from the two versions  while building an uber-jar   It will select the  nearest  version based on its dependency mediation rules and will output a warning  We have a duplicate class     If a method class signature changes between the versions  it can cause a java lang IncompatibleClassChangeError exception if the incorrect version is used at runtime   Advanced  If A must use v1 of C and B must use v2 of C  then we must relocate C in A and B s poms to avoid class conflict  we have a duplicate class warning  when building the final  project that depends on both A and B

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My answer  I believe  will be Intellij specific     I had rebuilt clean  even going as far as to manually delete the  out  and  target  dirs   Intellij has a  invalidate caches and restart   which sometimes clears odd errors  This time it didn t work  The dependency versions all looked correct in the project settings- modules menu   The final answer was to manually delete my problem dependency from my local maven repo   An old version of bouncycastle was the culprit I knew I had just changed versions and that would be the problem  and although the old version showed up no where in what was being built  it solved my problem   I was using intellij version 14 and then upgraded to 15 during this process

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Another situation where this error can appear is with Emma Code Coverage   This happens when assigning an Object to an interface  I guess this has something to do with the Object being instrumented and not binary compatible anymore   http   sourceforge net tracker  func detail amp aid 3178921 amp group id 177969 amp atid 883351  Fortunately this problem doesn t happen with Cobertura  so I ve added cobertura-maven-plugin in my reporting plugins of my pom xml

[java] What causes java.lang.IncompatibleClassChangeError?

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