Why am I getting a NoClassDefFoundError in Java

Question

I am getting a NoClassDefFoundError when I run my Java application   What is typically the cause of this

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I got NoClassDefFound errors when I didn t export a class on the  Order and Export  tab in the Java Build Path of my project   Make sure to put a checkmark in the  Order and Export  tab of any dependencies you add to the project s build path   See Eclipse warning  XXXXXXXXXXX jar will not be exported or published  Runtime ClassNotFoundExceptions may result

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I got this message after removing two files from the SRC library  and when I brought them back I kept seeing this error message   My solution was  Restart Eclipse  Since then I haven t seen this message again  -

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One interesting case in which you might see a lot of NoClassDefFoundErrors is when you    throw a RuntimeException in the static block of your class Example Intercept it  or if it just doesn t matter like it is thrown in a test case  Try to create an instance of this class Example     static class Example       static           thisThrowsRuntimeException             static class OuterClazz        OuterClazz             try               new Example              catch  Throwable ignored      simulating catching RuntimeException from static block                DO NOT DO THIS IN PRODUCTION CODE  THIS IS JUST AN EXAMPLE in StackOverflow                    new Example      this throws NoClassDefFoundError           NoClassDefError will be thrown accompanied with ExceptionInInitializerError from the static block RuntimeException     This is especially important case when you see NoClassDefFoundErrors in your UNIT TESTS   In a way you re  sharing  the static block execution between tests  but the initial ExceptionInInitializerError will be just in one test case  The first one that uses the problematic Example class  Other test cases that use the Example class will just throw NoClassDefFoundErrors

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If someone comes here because of java lang NoClassDefFoundError  org apache log4j Logger error  in my case it was produced because I used log4j 2  but I didn t add all the files that come with it   and some dependency library used log4j 1  The solution was to add the Log4j 1 x bridge  the jar log4j-1 2-api- lt version gt  jar which comes with log4j 2  More info in the log4j 2 migration

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NoClassDefFoundError can also occur when a static initializer tries to load a resource bundle that is not available in runtime  for example a properties file that the affected class tries to load from the META-INF directory  but isn   t there  If you don   t catch NoClassDefFoundError  sometimes you won   t be able to see the full stack trace  to overcome this you can temporarily use a catch clause for Throwable  try          Statement s  that cause s  the affected class to be loaded   catch  Throwable t        Logger getLogger  quot  lt logger-name gt  quot   info  quot Loading my class went wrong quot   t

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I have found that sometimes I get a NoClassDefFound error when code is compiled with an incompatible version of the class found at runtime   The specific instance I recall is with the apache axis library   There were actually 2 versions on my runtime classpath and it was picking up the out of date and incompatible version and not the correct one  causing a NoClassDefFound error   This was in a command line app where I was using a command similar to this     set classpath  classpath  axis jar   I was able to get it to pick up the proper version by using   set classpath axis jar  classpath

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I fixed my problem by disabling the preDexLibraries for all modules   dexOptions           preDexLibraries false

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I got this error when I add  Maven dependency of another module to my project  the issue was finally solved by add -Xss2m to my program s JVM option It s one megabyte by default since JDK5 0   It s believed the program does not have enough stack to load class

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NoClassDefFoundError In Java  Definition     Java Virtual Machine is not able to find a particular class at runtime which was available at compile time  If a class was present during compile time but not available in java classpath during runtime      Examples    The class is not in Classpath  there is no sure shot way of knowing it but many times you can just have a look to print System getproperty  java classpath   and it will print the classpath from there you can at least get an idea of your actual runtime classpath  A simple example of NoClassDefFoundError is class belongs to a missing JAR file or JAR was not added into classpath or sometimes jar s name has been changed by someone like in my case one of my colleagues has changed tibco jar into tibco v3 jar and the program is failing with java lang NoClassDefFoundError and I were wondering what s wrong  Just try to run with explicitly -classpath option with the classpath you think will work and if it s working then it s a sure short sign that someone is overriding java classpath  Permission issue on JAR file can also cause NoClassDefFoundError in Java  Typo on XML Configuration can also cause NoClassDefFoundError in Java  when your compiled class which is defined in a package  doesn   t present in the same package while loading like in the case of JApplet it will throw NoClassDefFoundError in Java    Possible Solutions    The class is not available in Java Classpath  If you are working in J2EE environment than the visibility of Class among multiple Classloader can also cause java lang NoClassDefFoundError  see examples and scenario section for detailed discussion  Check for java lang ExceptionInInitializerError in your log file  NoClassDefFoundError due to the failure of static initialization is quite common  Because NoClassDefFoundError is a subclass of java lang LinkageError it can also come if one of it dependency like native library may not available  Any start-up script is overriding Classpath environment variable  You might be running your program using jar command and class was not defined in manifest file s ClassPath attribute    Resources   3 ways to solve NoClassDefFoundError  java lang NoClassDefFoundError Problem patterns

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Java was unable to find the class A in runtime   Class A was in maven project ArtClient from a different workspace  So I imported ArtClient to my Eclipse project   Two of my projects was using ArtClient as dependency  I changed library reference to project reference for these ones  Build Path -  Configure Build Path    And the problem gone away

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While it s possible that this is due to a classpath mismatch between compile-time and run-time  it s not necessarily true   It is important to keep two or three different exceptions straight in our head in this case    java lang ClassNotFoundException  This exception indicates that the class was not found on the classpath   This indicates that we were trying to load the class definition  and the class did not exist on the classpath  java lang NoClassDefFoundError  This exception indicates that the JVM looked in its internal class definition data structure for the definition of a class and did not find it   This is different than saying that it could not be loaded from the classpath   Usually this indicates that we previously attempted to load a class from the classpath  but it failed for some reason - now we re trying to use the class again  and thus need to load it  since it failed last time   but we re not even going to try to load it  because we failed loading it earlier  and reasonably suspect that we would fail again    The earlier failure could be a ClassNotFoundException or an ExceptionInInitializerError  indicating a failure in the static initialization block  or any number of other problems   The point is  a NoClassDefFoundError is not necessarily a classpath problem

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I had the same problem  and I was stock for many hours   I found the solution  In my case  there was the static method defined due to that  The JVM can not create the another object of that class   For example   private static HttpHost proxy   new HttpHost proxyHost  Integer valueOf proxyPort    http

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In my case I was getting this error due to a mismatch in the JDK versions  When I tried to run the application from Intelij it wasn t working but then running it from the command line worked  This is because Intelij was attempting to run it with the Java 11 JDK that was setup but on the command line it was running with the Java 8 JDK  After switching that setting under File   Project Structure   Project Settings   Project SDK  it worked for me

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Two different checkout copies of the same project  In my case  the problem was Eclipse s inability to differentiate between two different copies of the same project  I have one locked on trunk  SVN version control  and the other one working in one branch at a time  I tried out one change in the working copy as a JUnit test case  which included extracting a private inner class to be a public class on its own and while it was working  I open the other copy of the project to look around at some other part of the code that needed changes  At some point  the NoClassDefFoundError popped up complaining that the private inner class was not there  double-clicking in the stack trace brought me to the source file in the wrong project copy   Closing the trunk copy of the project and running the test case again got rid of the problem

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In case you have generated-code  EMF  etc   there can be too many static initialisers which consume all stack space    See Stack nbsp Overflow question How to increase the Java stack size

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I was using Spring Framework with Maven and solved this error in my project   There was a runtime error in the class  I was reading a property as integer  but when it read the value from the property file  its value was double   Spring did not give me a full stack trace of on which line the runtime failed  It simply said NoClassDefFoundError  But when I executed it as a native Java application  taking it out of MVC   it gave ExceptionInInitializerError which was the true cause and which is how I traced the error    xli s answer gave me insight into what may be wrong in my code

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This is the best solution I found so far   Suppose we have a package called org mypackage containing the classes    HelloWorld  main class    SupportClass  UtilClass   and the files defining this package are stored physically under the directory D  myprogram  on Windows  or  home user myprogram  on Linux    The file structure will look like this    When we invoke Java  we specify the name of the application to run  org mypackage HelloWorld  However we must also tell Java where to look for the files and directories defining our package  So to launch the program  we have to use the following command

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I have had an interesting issue wiht NoClassDefFoundError in JavaEE working with Liberty server   I was using IMS resource adapters and my server xml had already resource adapter for imsudbJXA rar  When I added new adapter for imsudbXA rar  I would start getting this error for instance objects for DLIException  IMSConnectionSpec or SQLInteractionSpec  I could not figure why but I resolved it by creating new server xml for my work using only imsudbXA rar   I am sure using multiple resource adapters in server xml is fine  I just had no time to look into that

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The technique below helped me many times   System out println TheNoDefFoundClass class getProtectionDomain   getCodeSource   getLocation       where the TheNoDefFoundClass is the class that might be  lost  due to a preference for an older version of the same library used by your program  This most frequently happens with the cases  when the client software is being deployed into a dominant container  armed with its own classloaders and tons of ancient versions of most popular libs

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Everyone talks here about some Java configuration stuff  JVM problems etc   in my case the error was not related to these topics at all and had a very trivial and easy to solve reason  I had a wrong annotation at my endpoint in my Controller  Spring Boot application

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Make sure this matches in the module app and module lib   android       compileSdkVersion 23     buildToolsVersion  22 0 1      packagingOptions              defaultConfig           minSdkVersion 17         targetSdkVersion 23         versionCode 11         versionName  2 1

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I had this error but could not figure out the solution based on this thread but solved it myself  For my problem I was compiling this code  package valentines   import java math BigInteger  import java util ArrayList   public class StudentSolver       public static ArrayList lt Boolean gt  solve ArrayList lt ArrayList lt BigInteger gt  gt  problems              DOING WORK HERE                    public static void main String   args             TESTING SOLVE FUNCTION               I was then compiling this code in a folder structure that was like  ProjectName valentines Compiling it worked fine but trying to execute  java StudentSolver I was getting the NoClassDefError  To fix this I simply removed  package valentines  I m not very well versed in java packages and such but this how I fixed my error so sorry if this was already answered by someone else but I couldn t interpret it to my problem

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I get NoClassFoundError when classes loaded by the runtime class loader cannot access classes already loaded by the java rootloader  Because the different class loaders are in different security domains  according to java  the jvm won t allow classes already loaded by the rootloader to be resolved in the runtime loader address space   Run your program with  java -javaagent tracer jar  YOUR java ARGS    It produces output showing the loaded class  and the loader env that loaded the class   It s very helpful tracing why a class cannot be resolved      ClassLoaderTracer java    From  https   blogs oracle com sundararajan entry tracing class loading 1 5  import java lang instrument    import java security        manifest mf    Premain-Class  ClassLoadTracer     jar -cvfm tracer jar manifest mf ClassLoaderTracer class     java -javaagent tracer jar         public class ClassLoadTracer        public static void premain String agentArgs  Instrumentation inst                 final java io PrintStream out   System out          inst addTransformer new ClassFileTransformer                 public byte   transform ClassLoader loader  String className  Class classBeingRedefined  ProtectionDomain protectionDomain  byte   classfileBuffer  throws IllegalClassFormatException                    String pd    null    protectionDomain     null    protectionDomain getCodeSource   toString                    out println className     loaded by     loader     at     new java util Date       in     pd                       dump stack trace of the thread loading class                  Thread dumpStack                        we just want the original  class bytes to be loaded                     we are not instrumenting it                    return null

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This error can be caused by unchecked Java version requirements   In my case I was able to resolve this error  while building a high-profile open-source project  by switching from Java 9 to Java 8 using SDKMAN    sdk list java sdk install java 8u152-zulu sdk use java 8u152-zulu   Then doing a clean install as described below     When using Maven as your build tool  it is sometimes helpful -- and usually gratifying  to do a clean  install  build with testing disabled   mvn clean install -DskipTests   Now that everything has been built and installed  you can go ahead and run the tests   mvn test

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Here is the code to illustrate java lang NoClassDefFoundError  Please see Jared s answer for detailed explanation   NoClassDefFoundErrorDemo java  public class NoClassDefFoundErrorDemo       public static void main String   args            try                  The following line would throw ExceptionInInitializerError             SimpleCalculator calculator1   new SimpleCalculator              catch  Throwable t                System out println t                        The following line would cause NoClassDefFoundError         SimpleCalculator calculator2   new SimpleCalculator               SimpleCalculator java  public class SimpleCalculator       static int undefined   1   0

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It could also be because you copy the code file from an IDE with a certain package name and you want to try to run it using terminal  You will have to remove the package name from the code first  This happens to me

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This is caused when there is a class file that your code depends on and it is present at compile time but not found at runtime  Look for differences in your build time and runtime  classpaths

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Update  https   www infoq com articles single-file-execution-java11     In Java SE 11  you get the option to launch a single source code file directly  without intermediate compilation  Just for your convenience  so that newbies like you don t have to run javac   java  of course  leaving them confused why that is

[java] Why am I getting a NoClassDefFoundError in Java?

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