Eclipse error Could not find or load main class

Question

I know there are many duplicates of this question  but I have looked at them all  and none of them have solved the issue   I am trying to run a class that has a main function  I have cleaned the project  checked the classpath for      added the bin folder to the classpath under run configurations  I m not sure what else to try because the class is certainly in the source folder   Could someone please help me with this issue   package testIt   public class MemoryVisualizerApp extends Application   public static void main String   args        launch args        Setup the scene and launch with given properties  Override public void start Stage primaryStage  throws IOException      Parent root   FXMLLoader load getClass   getResource   MemoryVisualizer fxml         Scene scene   new Scene root  650  300         Set whether the screen should be re-sizable  possibly best size   default      primaryStage setResizable true       primaryStage setMinHeight 300       primaryStage setMinWidth 550       primaryStage setTitle  Memory Usage        primaryStage setScene scene       scene getStylesheets   add  testIt MemoryVisualizer css        primaryStage setOnCloseRequest new EventHandler lt WindowEvent gt                   public void handle WindowEvent e                   Currently the threads continue running after window is closed  Looking for               a way to stop the app threads when window closed without stopping the program                          primaryStage show        primaryStage show           This code is located within a package  withing the src folder  It utilizes some JavaFX files that arent shown but that shouldnt be an issue   This is the error  Error  Could not find or load main class testIt MemoryVisualizerApp

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if your package name is same with your class name this problem will occur

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I had the same problem with correct  classpath file  and soon found actually it s not the  classpath file counted  after I fixed this issue  I replace the workable  classpath file with the original one  the project still worked  which means the  classpath file was not the case   Since it s a Maven project  all I did is    mvn eclipse clean delete eclipse project import the project done   hope it helps

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Just go to your Package Explorer and press F5  or for some laptops fn F5  The reason is that eclipse thinks that the files are somewhere  but the files are actually somewhere else  By refreshing it  you put them both on the same page  Don t worry  you won t lose anything  but if you want to be extra careful  just back up the files from your java projects folder to somewhere safe

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I had the same issue and I could not start any project with main   methods   I tried almost everything mentioned above  but it turned out that I had a little mistake in my pom xml file   You can check this file too

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you  should add bin folder - run- run Configuration tab classpath advanced button - add folder -  choose bin folder   yourproyect bin

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Found This while searching  and it was after I updated my Java that the problem seemed to occur   In Eclipse from your project   Right-click on your project Click Properties Java build path  Libraries  Remove the  JRE System Library J2SE 1 4   Click Add Library - gt  JRE System Library Select the new  Execution Environment  or Workspace default JRE

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If you create a java class with public static void main String   args   Eclipse will run that main method for you by right clicking on the file itself  or on the file in the project explorer  then choosing       Run As  -   Java Application     Once you do this  Eclipse stores information about your class  so you can easily run the class again from the Run As menu  Green Play Button on the toolbar  or from the Run Configurations dialog   If you subsequently MOVE the java class  manually  or however   then again choose       Run As  -   Java Application     from the new location  Eclipse will run the original stored configuration  attempt to invoke this class from its original location  which causes this error    SOLUTION  For me  the fix was to go to the run configurations   Green Play Button -  Run Configurations  and remove all references to the class  The next time you run       Run As  -   Java Application     Eclipse will write a new configuration for the moved class  and the error will go away

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I ran into this error today because I set up a hello world program and then cut and pasted a new program into the same file  To fix the problem of not finding hello world as the last was called I clicked Run-  Run Configurations and then under Main Class I clicked search and it found my new class name and replaced it with the correct new name in the text that I pasted  This is a newbie problem I know but it is also easy to fix  I hope this helps someone  Douglas

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I too faced same problem   Simple solution is   delete project  not source files please   close eclipse--   go to project folder--    remove classpath and project file    then open Eclipse and create project in same location

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If You are using eclipse then the following steps will solve your problem      Go to Run -  Run Configurations -  Main Class Search -  Locate your class manually -  Apply -  Run

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I just ran into that problem  The cause    not sure  However  only happened after I added a new jvm  My solution     went to run configurations   - run- run configurations   In the Classpath tab    Select Advanced  Add where Eclipse usually put the   class for the projects  which is in bin  So I added the bin directory for the project    I hope it helps someone out there  It took me time to figure this out

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Sometimes  it might have a very simple solution   You have perhaps added a new version of the existing  jar file and forgot to remove the old version of the same  jar file   Now try removing the old jar files  that are marked in red  in the Build Path   Configure Build Path

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Happened to me when I changed installed JREs to JDK7 instead of JRE7  Everything compiled but I couldn t run anything from Eclipse  eclipse-error-could-not-find-or-load-main-class   Fix  going back to previous JRE7

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I am assuming that you had imported the project into your desktop eclipse installation  If that is the case  you should just select Project   Clean  Then rebuild your project  Worked like a charm for me

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Check if you have included any missing dependencies  In my case I ve imported json jar  which is no longer present in that path   Removing it from Libraries helped   To navigate to Libraries  Right click on project - gt  Properties

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I was having the same problem  I was having a maven project  According to my knowledge  it was because i had cleaned the project and there were no class files generated  I did mvn compile and it was started running

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I had similar problem  my standalone java program was not working  I had other compilation error in my workspace in other unrelated java files  After removing all compilation errors I could run my standalone java program

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Well the following worked for me      Went into the project folder  inside workspace  Then  deleted the bin folder Then  Cleaned project   projects  in Eclipse  built run from Eclipse

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I had a very strange reason for this error   Some of the files referenced in the local Maven repository     m2      were corrupt   After deleting these and then rebuilding the application  it worked   Using a newer version of Maven exposed the corrupt files

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Follow The Steps it Works for me   1 Remove Configure build path from eclipse Build Path  2 Refresh  3 add configure Build Path- Source- add Folder- check src ok

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I faced the similar problem  a workaround is to open up a terminal  go to project folder and run  java cp target  lt your jar artifact jar gt   lt com your package YourMainClass gt

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I run into the same problem  but in my case it was caused by missing  empty  source folder  it exists in original project  but not in GIT repository because it s empty    After creating the missing folder everything works

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I had the same issue and solved it using   Eclipse Mars Egit Github Maven Project   The Problem was that i made my maven project available to github  It moved my project to my github folder    Solution     Close Eclipse Delete the metadata folder inside your workspace Restart Eclipse   Start screen will be displayed     Close the start screen Rightclick into package explorer Chose  import maven project   Navigate to your github folder and import the maven project     After this my project compiled with success

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Mostly this happens  because Eclipse cleans the  class files  but don t build them again  Check the bin folder  it should be empty  Then you should check  is there anything else  which is causing build ti fail  You might have added some jars in classpath  which Eclipse might not be able to find

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Check the workspace error log  Windows-  Show View -  Error log    If you see any of the jar s imported is corrupted  remove the corresponding repository folder and re-import again

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I just had this problem after first having the problem of Windows 8 refusing to update my path no matter what I set JAVA HOME to - java -version reported the last JDK instead of the one I stored in JAVA HOME  I finally got that to work by putting   JAVA HOME  bin   at the front of the path environment variable instead of at the end  Then I launched Eclipse and all the sudden it could not find my main class when it worked fine before this  What I did to fix it was went into the project properties  removed the existing JRE library from the libraries tab  added a new JRE by selecting the  Add Library  button and then followed the prompts to install JRE 7 as my default JRE  Now all is back to working

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To solve this error do the following steps   Step 1  Open the  project file   Step 2  Check two tags         a   lt buildSpec gt       b   lt natures gt    Step 3  If the above-mentioned tags do not include any content then surely the above error is going to occur   Step 4  Add the following content to each tag in order to resolve the above error   For  lt buildSpec gt      lt buildSpec gt       lt buildCommand gt           lt name gt org eclipse jdt core javabuilder lt  name gt           lt arguments gt           lt  arguments gt       lt  buildCommand gt   lt  buildSpec gt    For  lt natures gt      lt natures gt       lt nature gt org eclipse jdt core javanature lt  nature gt   lt  natures gt    Step 5  Save your file by hitting ctrl   s   Step 6  For safe side just close the project once and reopen it   Step 7  That s it  You are ready to rock     Please mention in comments if the solution was helpful   Thank you

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I faced the same error  the error was in one of the imported  external jars  After removing that jar project worked for me

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In your classpath you re using an absolute path but you ve moved the project onto a new machine with quite possibly a different file structure   In your classpath you should therefore  and probably in general if you re gonna bundle JARS with your project   use relative pathing   In your  classpath change    lt classpathentry kind  lib  path  C  Users Chris Downloads last fm-bindings-0 1 1 jar  sourcepath     gt  lt classpathentry kind  lib  path  C  Users Chris Downloads last fm-bindings-0 1 1 jar  sourcepath     gt    to    lt classpathentry kind  lib  path  last fm-bindings-0 1 1 jar   gt

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If you are using maven Project     First please clean your project  then installed maven- if build success then run your project   then project will be working fine   thanks

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I had the same problem  In my case I did the following  to resolve it    Select the project in the Eclipse IDE  right click  and open properties dialog  Select  Java Build Path  item on the left panel of the Properties dialog  Select the  Libraries  tab  on the right hand panel   Remove the libraries  jars   which are marked red  or fix the path  Save the Properties dialog  After removing the  Not found  libraries  Eclipse run debug started working   The  Not found  message would also show up in the  Problems  pane  which you can open using  Window- Show View- Problems  command sequence  This pane gives you useful messages  The same message might show up for many reasons  other than what I encountered     Observation  The classes directory in my case was not created  which means that the javac failed  On command line also  javac works the same way  if you have multiple java files in the same invocation of javac  and one java file encounters a problem  then no class files are created    Which means Eclipse puts all the java files in the project with single invocation of javac    Now if there are no class files generated  obviously  the message now makes sense   The compile errors are also shown in the  Problems  pane    Now this would be the case if there is a compile error   If just a jar file which is not used at all  is on the classpath  there should not be any problem    Even if my project had problems  I ignored it  because I was just testing a single class  and was thinking that only that file would get compiled and run  because it was a standalone test  without any dependencies    But that is not the case with Eclipse  I wish they did it that way  As you can see lot of people got burnt this way    Thanks

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I spent tenths of hours trying to solve this  and what only helped me at the end was to notice that I had in my packages some files  text files  with the same name  like TODO  README and IMPORTANT  I went through every package of my project renaming those files  like TODO packagename1  TODO packagename2     and when finished  I closed Eclipse and restarted it again  Then worked

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Check that your project has a builder by either    check project properties  in the  package explorer   right click on the project  select  properties    there the second section is  Builders   and it should hold the default  Java Builder  or look in the   project  file  in     workspace yourProjectName  project  the section  buildSpec  should not be empty    There must be other ways  but what I did was    shut down eclipse edit the   project  file to add the  buildSpec  section restart eclipse   A proper minimal java   project  file should look like    lt  xml version  1 0  encoding  UTF-8   gt   lt projectDescription gt           lt name gt myProjectName lt  name gt           lt comment gt  lt  comment gt           lt projects gt           lt  projects gt           lt buildSpec gt                   lt buildCommand gt                           lt name gt org eclipse jdt core javabuilder lt  name gt                           lt arguments gt                           lt  arguments gt                   lt  buildCommand gt           lt  buildSpec gt           lt natures gt                              lt nature gt org eclipse jdt core javanature lt  nature gt           lt  natures gt         lt  projectDescription gt

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I just encountered the same problem as yours and I followed Kumar s directions and it worked out  One thing to add  you need to make sure that after you go to the correct main class  check the  Classpath  and your project name should be existed under the  User Entries   If not  add your project to the directory then you re good to go

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Removing the JRE System Library and adding the default one worked for me

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I had the same problem after I created new package  tables   in my project   I went to Window - gt  Show View - gt  General - gt  Error Log and Ive read error   JavaBuilder handling ImageBuilderInternalException while building  PizzaService  org eclipse core internal resources ResourceException  Resource   PizzaService bin tables  already exists    as it turned out I had a text file in another source folder with the same name as this new package  So I ve changed text file name from  Tables  to  Tabless  and I could run my project again   Hope this helps

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I recieved this error aswell  just after moving some resources  Checking the error log  I saw that Eclipse couldn t make a build since it couldn t remove a file folder  Try manually removing the  bin   or whatever it s called for you  folder   That did the trick for me  at least

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I was also getting same message That is due to the workspace problem Create one new workspace and try there once  I think it will works

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I followed several of the less drastic suggestion here to no avail  Then it dawned on me that Eclipse was confused because I had made a backup copy of my src project folder   It was compiling all these  copy of  folders    java files and I noticed the subfolders for them in my bin folder   I moved the backup elsewhere  got rid of the extraneous class files  did a Project   Clean  and everything was back to normal

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A very simple fix coul   d be  delete a commented error in the pom xml    I don   t now why  but the error coul   d persist in the pom  even if you comment it   In my case  it was an innecesary scope tag for mockit or whole dependency of mockit  all commented    It was sufficent delete the commented lines and save the pom

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In your Eclipse Preferences - gt  java - gt  Installed JREs - gt  Select the Java SE the jdk which you have on your machine and add the JDK

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This happened to me  I noticed that someone said I have to create an entire new WORKSHOP  Why  Because I installed a newer JRE version and that won t allow other previous versions to run on it  So all those old files I have become useless in a way  Not really  Just copy and paste it to new class and change it to an unused class name

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Similar thing happened to me few times  the only way I knew to fix this was to remove the metadata folder  Fortunately I have found another way   Try going to project properties   Java Build Path   Order And Export tab   select all  or try to play with check boxes there    This should cause complete project rebuild and Eclipse to see main class   Addition  I have noticed that this bug occurs when you have many projects in a work space and some of them is configured wrong red exclamation mark appears   Fixing project build path and other settings even if this project is not related to the one you have problems with  should fix an issue

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this could cause of jdk libraries if you had imported into jre   this happen to me   so check installed jre jars  in eclipse click on Windows   Preferences   Java   Installed Jres   click on Jre and edit after that look into jar list make sure none is of jdk or corrupted

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I came across the same problem  You might get this error in many situations like below    Some dependency problem in your pom xml The run configuration may not have proper configuration  You might want to delete the existing one and create the new one like suggested in other answers  You may want to try like mvn clean  mvn build and other options  You may want to delete the project and import it again  You may want to restart Eclipse and check your luck if it works    Here  the list of hit and trial goes on  Believe me the tool Eclipse is not that stupid  It is quite smart to find errors even at compile time  I tried all ways mentioned above  but none worked for me    The main problem which worked for me was JRE version which was somehow got set to default  JRE System Library  jre1 5    I reset it to jre1 8   which I had installed in my machine   I don t commit that this is only the solution to this problem but yes this could be one of the solution  So keep an eye on JRE version

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Rebuilding using the command line has fixed this issue for me multiple times   For example  running ant build  for an Ant project  or mvn build  for a Maven project  will fix eclipse once it succeeds

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Project files using a custom archive in the build path  to fix -  go into the class path file  find and remove the entry then collect a new copy of the archive and add it to the build path again  You ll need to rebuild the project and to check the  run configurations  after

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I faced similar problem in my maven webapp project after spending nearly one hour   I found a solution which worked for me  I typed the following maven command and It worked  mvn clean install -U   I dont know the exact reason behind it

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I had the same problem  Spent few hours and finally changed my workspace back to local folder and everything works now  Maybe saves some time for others  Jon

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I ran into the same error today  I refactored my project name and then refactored it back to the old name and it ran just fine after that

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I was using eclipse oxygen and the problem persists everytime  Later i found that if your Eclipse workspace is under the directory with non ascii characters then somehow  javaw exe couldn t reach the bin directory  Suppose your directory name is Work Hello the remove underscore sign and clean the project and run configurations  This worked for me  Reference  https   www eclipse org forums index php t 1093209

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These are the simple steps  which helped me to solve this problem    Close the eclipse Delete   metadata  folder in your work-space   may be hidden folder  Open the eclipse  it will automatically create   metadata  folder in your work-        space  Try to run the program

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Try also renaming the package before changing the configuration or reinstalling   I got this weird error without having changed anything else than a few lines of code  Rebuilding did not work  Eclipse would not re-create the class even though the bin folder was empty  After renaming the package from test to test1 Eclipse started rebuilding and everything was fine

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Try to check first in the Problems window the errors you have  It is most likely it  Then check in the Configure Build Path    window under Order and Export for errors in jars and libraries  missing  duplicates  etc     Fixing the problems will fix the class-loading issue

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What I ended up doing is in Eclipse  copy the entire project and paste it again  and give it a different name of course   Then run your copied project  It should ask if you want it to run as a Java Applet or as a Java Application  Click on Java Application and it should work again  Then you can remove the original project and rename your current project to its original name if you wish

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I was getting the same message and I solve the problem moving out two dependencies from my pom xml called  org slf4j   After that It worked perfectly

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The same error I am facing in my eclipse and going through above all did not help me out  So here are the steps you can do   Check the problems- Windows- gt Show view- gt others- gt problem if you find something their errors saying  quot A cycle was detected in the build path of project xxx - Build Path Problem quot   then Do simple thing  Mark Circular dependency as a warning  Windows - gt  Preferences - gt  Java- gt  Compiler - gt  Building - gt  Circular Dependencies and it will fix your problem  Never forget to clean the project after that  Project- gt clean  Hope this will help

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If your code is good and you know you re having an Eclipse problem  this will solve it   You could simply delete  yourproject  classpath    yourproject  project   and  yourworkspace  metadata  Someone else mentioned this option  It will blow up your entire workspace though  Instead    Delete  classpath and  project from your project Delete your project in eclipse  DO NOT check delete project contents on disk  Now  in a file explorer  go into  yourworkspace  metadata  Search for  yourprojectname Delete everything you find  It should be safe-ish to delete anything in the  metadata directory  In eclipse  File   Import   General   Projects from Folder or Archive    yourproject   finish Right click your project   properties   Java Build Path   Source tab Select all source folders  remove   Add folder  select src  whatever your src folder is called  and add it Go to libraries tab Add any jars to your build path here  There should be no more errors on your project now  Run your project like you normally would

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I was running through the similar problems in my small java snippet  Here is what I did    I copied all the content in the Main class  Deleted the Main class Greeter  Right click -  Created a new Java class with name Greeter  a  checked include main method when creating class voila     I was able to run as Java application by right clicking on the main class Greeter java    Just out of curiosity I again tried deleting the Greeter class and creating new class without checking main method  and it did not show me run as Java application option in right click

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This just happened to me today after updating my JRE  I cleaned the project and it started working again   Project - gt  Clean will remove any existing class files and completely rebuild the project  There s more information on Eclipse s clean function here

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I had this same problem with Eclipse-Mars  I had a working project then put it in my Git repository  That broke the execution  I guess because the actual Java files got moved to the git location and no longer existed in my workspace   I did a Maven Update and it now works

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Actually I found the real Root Cause for this issue  by going to add each  jar files manually one by one  because the following answer within the same thread  suggests you to do so   Cause  You know as we are humans  we are really lazy creatures and that s why we have an option to  Select All  and also shortcut keys to perform that  So when I have to add around 30  jar files for a PDF generation required app  I did go in this way      Right Click on Project -  Properties -  Java Build Path    selected  Libraries  tab in it  then Add JARs      browsed through the directories tree and  my JARs and the licence txt files was in projects  lib  folder  within the  lib  folder  I selected All the files and Added  Can you guess what has been the wrong  It had successfully add all the files within the  lib  folder  But eclipse keeps trying to profess any of the text files you may have added as JAR file  in this way  So it can t build the links  This is the case    So you have two options    Select only the JAR files wherever you want and don t be too lazy to add text and other types of files  or  Select all files within a specific folder where you wanna add JARs from  and then remove one by one  which are non-JAR files    Note  If you have added any of non-JAR files to the project in that way as you were trying to add  libraries   it will show you something like the following     and keep trying to compile and at the end  it will give you the following error      Error  Could not find or load the main class er waterapp some MainFileGivenByConfigaration    MainFileGivenByConfigaration could be any class which you might have selected from Configuration to be take as the starting point of the app    So this is it    Hope I may have had the chance to help some one out there and also save him a lot of time   -   Cheers  Randika

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tl dr  Clean your entire Build Path and everything you ever added to it manually  This includes additional sources  Projects  Libraries    Project -  Clean Make sure Project -  Build automatically is active Project -  Properties -  Java Build Path -  Libraries  Remove any external libs you have ever added  Don t remove standard libraries like the JRE System Library  Try to run your main class now  The  class could not be found   load  error should be gone  Try adding your external libs jars one after each other    Reason behind this  The compiler had issues linking the libraries to the project  It failed and produced a wrong error message   In my case  it should have been something like  Could not add AutoHotkey dll to the build path  because that was what made the compiler fail     If this is still not working  have a look at the built-in ErrorLog of Eclipse      Window -  Show View -  General -  Error Log

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This problem is also caused when you have special characters in your workspace path  I had my workspace in my personal folder and its name was in Greek  so it didn t work  I changed my workspace  now contains only english characters in its path  and now the project is built without any problems

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Follow these steps    1 Delete your current run configuration  2 Go to the main class and run it by right clicking the mouse-- Run As-- Java Application   Then you will see an auto generated new run configuration

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Had the same problem  struggling with it for a while  couldn t find main class   I did Project -  Clean -  Clean all Projects  Cleaned everything  and tada  it compiled

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I found other solution in my case this problem  Eclipse- gt Preferences- gt Java- gt Installed JRE then press button Search  Select folder in Linux  usr then Eclipse found all JVM    Select another JVM too current  It is solved for my case

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Try to point the classpathentry output path in the  classpath file to target classes The classpath file is located in the project folder  Edit it manually   In my case  it was like this before      classpathentry kind  output  path  bin    I changed it to      classpathentry kind  output  path  target classes

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that s because you guys created the class one time with the main method  amp  after that may be you have been deleted that form or workplace  amp  still some of the files exist  i will suggest you to create that form or workspace again  amp  then delete it by clicking on it completely then after that if you created the some class like Runner class try to run it again

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My Main class could not be found or loaded problem is caused by an interesting reason    In our project  we are using Maven as build tool and my main class extends a class  which is on the class path but its scope was test  while the main class is not under the test package    If your main class extends a class  first try to run your main class by removing extends part  If it runs  you will at least understand that the problem is not because of run configuration or eclipse but the class  your main class extends

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This problem occurred for me when I deleted a  quot  jar quot  file from Eclipse project by right clicking on it and hitting  quot delete quot   not from  quot Build path quot    To solve  I tried the following steps   1- Right click on the project 2- Build Path -- gt  Configure Build Path 3- Libraries 4- Delete the jar file from there  I see a red mark beside it    I hope it is useful

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If all the solution does not work for you  it may be caused by missing libraries    Right click your project  Build Path -- gt  Configure Build Path -- gt  Java Build Path -- gt  Libraries Remove the missing libraries Go to your main class and run it

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I have checked all possible solutions including re-installation of JDK  eclipse as it worked for many people but unfortunately it didn t work for me  Also updated main class in pom xml but it didn t help  It took my sleep away  I was trying different options and suddenly the magic happened when I checked this checkbox  It might be helpful for many people so thought of sharing

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I too faced this issue today  Whatever new class I created with main method i faced the same issue  Then I checked the build path and saw that one of the java api jar file - nashorn was showing as missing  I put it back in the ext folder and it worked

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I deleted a jar file from the bin directory   Right click on your project - Properties then Libraries tab   There was a red flag in there   I removed the jar file from the Libraries and it worked

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Usually cleaning and rebuilding the project from Eclipse does the trick   However  when using Maven I have discovered times this does not work and I ve noticed the  target  folder of my maven project does not have anything under it  Running  mvn clean install  from the command line and refreshing the project in eclipse does the trick

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i had same problem but in my case firewall was blocking java directory path  make sure system firewall is allowing java directory path access

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For me  the reason that this error started showing up was due to classpath getting over the limit on windows  Then I discovered the option  Use temporary JAR to specify classpath  to avoid classpath length limitations    Selecting this option fixed the problem for me  The option resides in Run Debug Configuration  Classpath tab  see the image below

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If you are facing similar problem it has to do with the  Run Configurations  not working properly in Eclipse     Please right clik on your java class containing the main method  Go to Run As-  Run Configurations and put the correct patrameters Project should be the Project which contains the main class and Main class should be fuly qualified class name See the snapshots below for clarity It should wok fine then Basically you are creating a Run configuration and you can use that saved configuration for later use also

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Rename the class with Ctrl Shift R  Windows   it will change name of the class everywhere where it is referred  and then do the opposite procedure  In my case it was caused by identical class names in several projects within the environment and Eclipse had hard time to understand which is which

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I also had the same issue and was getting  Error  Could not find or load main class        I solved it as follows    Right clicked on my Java main class   Run As   Run Configurations  In the resultant popup box and Under Java Application your java file name would be selected mode    if not select it On the right side of the same box and under Classpath tab Clear all Bootstrap and User Entries  if any   Under Bootstrap Entries Click Advanced Button   Select Add Library Radio and click OK  In next  Add Library  box Select JRE System Library and provide your correct JRE location and click Finish   If it is not visible then u have to add it by clicking Installed JRE   Add button   Now you can see JRE System Library under BootStrap Entries Next User Entries   Click Add Projects Button   And then under Project Selection box check on your Project name   OK   The main java file should now work  Hope this may help someone who would be facing similar issues

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2 types of solutions exits for the same    1  Go to run configurations  - run- run configurations In the Classpath tab   Select Advanced Add where Eclipse usually put the   class for the projects  which is in bin  So I added the bin directory for the project    2  If first solution is not working then it means the jar you are pointing out to your project is taking the path of your local Maven repo which is not getting updated to your project so better you check the jar from that local maven repo and copy it paste it into new project simply or just download it from any site and configure it into your build path   I hope it helps

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It seems that the class is not compiled by Eclipse   Few pointers could be-   Check if the  class file exists in your output folder To know your output folder Right Click on Project- Properties- Java Build Path Check at bottom   Check if Project- build Automatically is checked in the menu  Check if the HelloWorld class is in src folder or not Right Click on Project- Properties- Java Build Path Check source tab

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I did all the things mentioned above  but none of them worked for me  My problem resolved as follows    Right click on your Project   Properties   JavaBuildPath   Libraries  Remove the jar file  having a red flag on it  If problem persists try the solution below  This worked for me when I faced this problem second time    Right-Click Project   Properties   Java Build Path   Libraries Remove Library Add Library   Choose the JRE System Library

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Same Problem occur with me I went to Project   Properties   Java BuildPath   There In order of export   I moved up my java main to the top priority

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I had this error  It was because I had static void main String   args  instead of public static void main String   args   I spent nearly an hour trying to figure that out   Note  The only difference is that I didn t declare main to be public

[java] Eclipse error "Could not find or load main class"

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