Java Unresolved compilation problem

Question

What are the possible causes of a  java lang Error  Unresolved compilation problem    Additional information    I have seen this after copying a set of updated JAR files from a build on top of the existing JARs and restarting the application  The JARs are built using a Maven build process   I would expect to see LinkageErrors or ClassNotFound errors if interfaces changed  The above error hints at some lower level problem   A clean rebuild and redeployment fixed the problem  Could this error indicate a corrupted JAR

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Make sure you have removed unavailable libraries  jar files  from build path

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I got this error multiple times and struggled to work out  Finally  I removed the run configuration and re-added the default entries  It worked beautifully

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The major part is correctly answered by Thorbj  rn Ravn Andersen   This answer tries to shed light on the remaining question  how could the class file with errors end up in the jar   Each build  mvn amp javac or eclipse  signals in its specific way when it hits a compile error  and will refuse to create a Jar file from it  or at least prominently alert you   The most likely cause for silently getting class files with errors into a jar is by concurrent operation of Maven and Eclipse   If you have Eclipse open while running a mvn build  you should disable Project   Build Automatically until mvn completes   EDIT  Let s try to split the riddle into three parts       1  What is the meaning of  java lang Error  Unresolved compilation   problem    This has been explained by Thorbj  rn Ravn Andersen  There is no doubt that Eclipse found an error at compile time       2  How can an eclipse-compiled class file end up in jar file created   by maven  assuming maven is not configured to used ecj for   compilation     This could happen either by invoking maven with no or incomplete cleaning  Or  an automatic Eclipse build could react to changes in the filesystem  done by maven  and re-compile a class  before maven proceeds to collect class files into the jar  this is what I meant by  concurrent operation  in my original answer        3  How come there is a compile error  but mvn clean succeeds    Again several possibilities   a  compilers don t agree whether or not the source code is legal  or  b  Eclipse compiles with broken settings like incomplete classpath  wrong Java compliance etc  Either way a sequence of refresh and clean build in Eclipse should surface the problem

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you just try to clean maven by command  mvn clean   and after that following command   mvn eclipse clean eclipse eclipse   and rebuild your project

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try to clean the eclipse project

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I had this error when I used a launch configuration that had an invalid classpath  In my case  I had a project that initially used Maven and thus a launch configuration had a Maven classpath element in it  I had later changed the project to use Gradle and removed the Maven classpath from the project s classpath  but the launch configuration still used it  I got this error trying to run it  Cleaning and rebuilding the project did not resolve this error  Instead  edit the launch configuration  remove the project classpath element  then add the project back to the User Entries in the classpath

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Your compiled classes may need to be recompiled from the source with the new jars   Try running  mvn clean  and then rebuild

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rewritten 2015-07-28  The default behavior of Eclipse when compiling code with errors in it  is to generate byte code throwing the exception you see  allowing the program to be run   This is possible as Eclipse uses its own built-in compiler  instead of javac from the JDK which Apache Maven uses  and which fails the compilation completely for errors   If you use Eclipse on a Maven project which you are also working with using the command line mvn command  this may happen  The cure is to fix the errors and recompile  before running again  The setting is marked with a red box in this screendump

[java] Java: Unresolved compilation problem

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