exception in thread main java lang NoClassDefFoundError

Question

The following program is throwing error   public class HelloWorld       public static void main String args              System out println  Hello World               CLASSPATH C  Program Files Java jdk1 6 0 18 bin   Path C  Program Files Java jdk1 6 0 18 bin   JAVAHOME C  Program Files Java jdk1 6 0 18 bin   Can you please tell me the root cause

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type the following in the cmd prompt  within your folder   set classpath  classpath

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If your package is helloworld you would go to parent dir of your package then run   java helloworld HelloWorld

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Try doing  javac Hello java   and then  if it comes up with no compiler errors  which it should not do because I cannot see any bugs in your programme   then type  java Hello

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if your Program java is in  src mypkg subpkg   directory   go to  src  dir   Then to compile use  javac mypkg subpkg Program java   To run use  java mypkg subpkg Program class

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Had the same problem tried above solutions but none worked  I had to go through my java code only to find that the main function could not be recognised since there was no space btw it and  String  ie initial code   public static void main String  args     working code   public static void main  String  args     Hope I helped someone

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I finally found this as a bug with Apache Netbeans editor     Below steps will remove the error      Rename the filename  amp  class to Abc Close the editor Reopen the editor Rename the filename  amp  class  from Abc  back to the previous name Now debug project  Ctrl F5  works fine   Hope that helps  if you are using new Apache Netbeans  not old Netbeans

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Java-File   package com beans   public class Flower              packages    gt  com beans  java class Name   gt  Flower java  Folder structure  assuming    gt  C  com beans Flower   both  java  class exist here    then there are two ways of executing it   1  Goto top Folder  here its C   gt         then   C  gt  java com beans Flower  2  Executing from innermost folder  beans  here  C  com beans  gt         then  C  com beans  gt  java -cp         com beans Flower

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If you want to  compile and execute  any java file that you have created using any IDE like eclipse   just run the below commands      Compile    javac Users dhiraj01 workspace Practice src PracticeLogic Logics java      Execute  java -classpath Users dhiraj01 workspace Practice src  PracticeLogic Logics

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The javadoc of NoClassDefFounError itself would be a good start  here   and then I ll suggest you clean and rebuild your project

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Add the jar in your classpath  For example  if you have NoClassDefFoundError for class XXXXXX  get the jar containing the class and add it to your classpath manually  It works for me  Hopefully it will work for you as well

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Run it like this   java -jar HelloWorld jar

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I found one another common reason  If you create the java file inside a package using IDE like eclipse  you will find the package name on the top of your java file like  package pkgName   If you try to run this file from command prompt  you will get the NoClassDefFoundError  error  Remove the package name from the java file and use the commands in the command prompt  Wasted 3 hours for this  -- Abhi

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I had this error because I had my files within a package  So my foo package I had to call like   java foo HelloWorld

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The CLASSPATH variable needs to include the directory where your Java programs  class file is   You can include     in CLASSPATH to indicate that the current directory should be included   set CLASSPATH  CLASSPATH

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Exception in thread  main  java lang NoClassDefFoundError     One of the places java tries to find your  class file is your current directory  So if your  class file is in C  java  you should change your current directory to that     To change your directory  type the following command at the prompt and press Enter   cd c  java     This    tells java that your classpath is your local directory   Executing your program using this command should correct the problem  java -classpath   HelloWorld

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I spent four hours trying various permutations  amp  search suggestions   At last  found this post that worked but not the best solution to change the original code to test it    Tried changing CLASSPATH  to include class libraries  set classpath JDKbin JDKlib JREbin JRElib myClassLib   Changed the current directory to parent directory package folder  and tired java  lt packageName gt   lt className gt  also tried the java     lt packageName gt   lt className gt    Neither worked    However first response alone worked  Thank you so much Abhi         I found one another common reason  If you create the java file inside a package using IDE like eclipse  you will find the package name on the top of your java file like  package pkgName   If you try to run this file from command prompt  you will get the NoClassDefFoundError error  Remove the package name from the java file and use the commands in the command prompt  Wasted 3 hours for this  -- Abhi    Curious if there is any other way to make it work without having to change the original code  Thank you

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I had this proplem I used maven  I just click maven projects ant then name  project- gt  plugins - gt  clean - gt  and button run

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See http   scottizu wordpress com 2013 08 28 fixing-the-exception-in-thread-main-java-lang-noclassdeffounderror-in-eclipse    This is the long form of the Java commands that can be run from a Windows command prompt    C  Program Files Java jdk1 6 0 18 bin javac exe  -classpath  C  Users Scott workspace myproject  com mycompany myapp HelloWorld java  C  Program Files Java jdk1 6 0 18 bin java exe  -classpath  C  Users Scott workspace myproject  com mycompany myapp HelloWorld    These commands can be run from any directory  meaning you don t have to be in the directory where your HelloWorld java file is  The first line compiles your HelloWorld java file  creating a HelloWorld class file    The second line runs the HelloWorld class file  The -classpath tells java where to look for the specified file in each command The Java compiler  javac exe  expects the location of the java file  relative to the classpath  ie the file is located at C  Users Scott workspace myproject com mycompany myapp HelloWorld java  Java  java exe  expects the package  ie com mycompany myapp  and class  HelloWorld   relative to the classpath  ie the file is located at C  Users Scott workspace myproject com mycompany myapp HelloWorld class    Notice the classpath has no slash at the end   The javac exe commands expects the file to end with   java    The java exe command expects the full class name and does not end with   class    There are a few ways to simplify these commands    You don t have to specify the entire path to java exe   Add Java to the Windows Path  Run- sysdm cpl- Advanced Tab- Environment Variables- Select Path- Edit- Append   C  Program Files Java jdk1 6 0 18 bin      Or you can append JAVA HOME and create that Environment Variable  You don t have to enter the entire classpath  ie  you can just use -classpath        Enter the directory you will be working in   cd  C  Users Scott workspace myproject   You can use the default package  put the HelloWorld java file directory in your working directory and don t use the Java package directive    If you make these changes you would run something like this  and you might be able to leave out -classpath        cd  C  Users Scott workspace myproject   javac -classpath     HelloWorld java java -classpath     HelloWorld

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Your CLASSPATH needs to know of the location of your HelloWorld class also    In simple terms you should append dot    means current directory  in the CLASSPATH if you are running javac and java commands from DOS prompt

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I had the same problem  and stumbled onto a solution with  Build Main Project F11    The ide brought up an  option  that I might want to uncheck  Compile on Save  in the Build   Compiling portion of the Project configuration dialog  Unchecking  Complile on Save  and then doing the usual  for me   Clean and Build  did the trick for me

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You can find information about required libraries inside pom xml  it is much easier to use tools like Apache Maven to build java applications        lt dependency gt           lt groupId gt org yaml lt  groupId gt           lt artifactId gt snakeyaml lt  artifactId gt           lt version gt 1 20 lt  version gt       lt  dependency gt       lt dependency gt           lt groupId gt org apache commons lt  groupId gt           lt artifactId gt commons-lang3 lt  artifactId gt           lt version gt 3 7 lt  version gt       lt  dependency gt       lt dependency gt           lt groupId gt org apache commons lt  groupId gt           lt artifactId gt commons-text lt  artifactId gt           lt version gt 1 2 lt  version gt       lt  dependency gt       lt dependency gt           lt groupId gt org apache commons lt  groupId gt           lt artifactId gt commons-math3 lt  artifactId gt           lt version gt 3 6 1 lt  version gt       lt  dependency gt       lt dependency gt           lt groupId gt com google guava lt  groupId gt           lt artifactId gt guava lt  artifactId gt           lt version gt 24 0-jre lt  version gt       lt  dependency gt        lt dependency gt           lt groupId gt org slf4j lt  groupId gt           lt artifactId gt slf4j-api lt  artifactId gt           lt version gt 1 7 25 lt  version gt       lt  dependency gt       lt dependency gt           lt groupId gt com google inject lt  groupId gt           lt artifactId gt guice lt  artifactId gt           lt version gt 4 2 0 lt  version gt       lt  dependency gt       lt dependency gt           lt groupId gt com google inject extensions lt  groupId gt           lt artifactId gt guice-assistedinject lt  artifactId gt           lt version gt 4 2 0 lt  version gt       lt  dependency gt

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Here is what finally worked     echo off set path  path  C  Program Files Java jdk1 7 0 71 bin  set classpath C  Program Files Java jdk1 7 0 71 lib  cd  lt packageDirectoryName gt  javac   trainingPackage HelloWorld java cd    java trainingPackage HelloWorld  REM  Make sure you are on the parent directory of the PackageName and not inside the    Packagedirectory when executing java

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The Problem here is the setting the environment and the running of the class file  a  To set the environment path run the following command  set path C  Program Files  x86  Java jdk1 7 0 bin b  run the program from the package like com test TestJavaClass  Command  java com test TestJavaClass  The general issue here is we run it either from inside the package like src package name  We should not include src  package name is enough

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Easy  amp  Simple solution  I solved this problem  NetBeans  by exporting the original project into zip file  deleting the original project directory and importing the project back from the zip file

[java] exception in thread 'main' java.lang.NoClassDefFoundError:

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