Could not find or load main class Error while running java program using cmd prompt

Question

I am running a simple  HelloWorld  Program  I get this error in the command prompt      Could not find or load main class HelloWorld    I have set the CLASSPATH and PATH variable in the system  In the cmd prompt  I am running from the directory where I have saved HelloWorld program  I can see the class name and the file name are same and also  class file created in the same directory  What else could be the problem   My sample program looks like this   package org tij exercises  public class HelloWorld     public static void main String   args           TODO Auto-generated method stub     System out println  Hello World

User · Answer

What s your CLASSPATH value   It may look like this         JAVA HOME  lib dt jar  JAVA HOME  lib tools jar    I guess your value does not contain this        So  ADD IT   When you done   restart CMD  That may works     For example the file HelloWorld java is in path  D  myjavatest org yz test and its package is  org yz test   Now  you re in path D  myjavatest  on the CMD line  Type this to compile it    javac org yz test HelloWorld java   Then  type this to run it     java org yz test HelloWorld   You may get what you want

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For a lot of us  at least for me  I think the class path hierarchy is not intuitive since I m working inside a directory structure and it feels like that ought to be it    Java is looking at the name of the class based on it s package path  not just the file path    It doesn t matter if  i m in the local directory   packagefoo MainClass  or a directory up   packagefoo   or  one down   packagefoo MainClass foo   The command  java packagefoo MainClass  is running off the root  CLASSPATH  which means something significant to Java  Then from there it traverses package names  not path names like us lay coders would expect    So if my CLASSPATH is set to  CWD    then  java packagefoo MainClass  will work   If I set the CLASSPATH to  CWD  packagefoo  then packagefoo MainClass can t be found   Always  java MainClass  means nothing  if it is a member of  package   until I rip out the java code  package packagefoo   and move the Class File up a directory    In fact if I change  package packagefoo   to  package foopackage   I have to create a subfolder under CLASSPATH foopackage or foopackage MainClass stops working again    To make matters worse  Between PATH  CLASSPATH  JAVAHOME  for Windows  JDeveloper  Oracle Database  and every user name it was installed under  I think a coder trying to just get something up fast ends up brute forcing path variables and structure until something works without understanding what it means   at least i did

User · Answer

I had the same problem  mine was a little different though I did not have a package name   My problem was the  Class Path for example   C  Java Example gt java -cp   HelloWorld    The -cp option for Java and from what I can tell from my experience  not much  but I encountered the error about 20 times trying different methods and until I declared the class Path I was receiving the same error   Vishrant was correct in stating that   represents current directory     If you need more information about the java options enter java -  or java -help I think the options are not optional   I just did some more research I found a website that goes into detail about CLASSPATH  The CLASSPATH must be set as an environment variable  to the current directory  lt      You can set it from the command line in windows      Set CLASSPATH to the current directory     prompt gt  set CLASSPATH     When you add a new environment setting you need to reboot before enabling the variable   But from the command prompt you can set it   It also can be set like I mentioned  at the beginning   For more info  and if your using a different OS  check  Environment Variables

User · Answer

Since you re running it from command prompt  you need to make sure your classpath is correct  If you set it already  you need to restart your terminal to re-load your system variables   If -classpath and -cp are not used and CLASSPATH is not set  the current directory is used      however when running  class files  you need to be in the folder which consist Java package name folders   So having the  class file in   target classes com foo app App class  you ve the following possibilities   java -cp target classes com foo app App CLASSPATH target classes java com foo app App cd target classes  amp  amp  java com foo app App   You can check your classpath  by printing CLASSPATH variable    Linux  echo  CLASSPATH Windows  echo  CLASSPATH    which has entries separated by     See also  How do I run Java  class files

User · Answer

faced the same problem  solved by following these steps   go to directory containing the package  org tij exercises   e g  in eclipse it may be your src folder  use java org tij exercises HelloWorld

User · Answer

I was getting the exact same error for forgetting to remove the  class extension when running the JAVA class  So instead of this   java myClass class   One should do this   java myClass

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I had a similar problem when running java on win10  instead of     java   hello Error  Could not find or load main class   hello   Run    java hello Hello  World

User · Answer

I faced the same problem and tried everything mentioned here   The thing was I didn t refresh my project in eclipse after class creation   And once I refreshed it things worked as expected

User · Answer

One reason for this error might be     Could not find or load main class  lt class name gt    Maybe you use your class name as different name and save the class name with another name you can save a java source file name by another name than class name  For example   class A      public static void main String args              System out println  Hello world              you can save as Hello java but   To Compile   javac Hello java    This will auto generate A class file at same location   Now To Run  nbsp   nbsp   nbsp   nbsp   java A

User · Answer

Create a folder org tij exercises and then move HelloWorld java file  Then run below command  javac -cp   org tij exercises HelloWorld java   AND  java -cp   org tij exercises HelloWorld

User · Answer

Execute your Java program using java -d   HelloWorld command   This command works when you have declared package     represent current directory

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I used IntelliJ to create my  jar  which included some unpacked jars from my libraries  One of these other jars had some signed stuff in the MANIFEST which prevented the  jar from being loaded  No warnings  or anything  just didn t work  Could not find or load main class  Removing the unpacked jar which contained the manifest fixed it

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I removed bin from the CLASSPATH  I found out that I was executing the java command from the directory where the HelloWorld java is located  i e    C  Users xyz Documents Java javastudy src org tij exercises gt java HelloWorld  So I moved back to the main directory and executed   java org tij exercises HelloWorld  and it worked  i e    C  Users xyz Documents Java javastudy src gt java org tij exercises HelloWorld  Hello World

User · Answer

I was facing similar issue but it was due to space character in my file directory where I kept my java class   Scenario given below along with solution      public class Sample        public static void main String   args            System out println  Hello world  Java                 My Sample java class was kept at Dir  D  Java Programs Sample java  NOTE  Package statement not present in java class   In command prompt  changed directory to  D  Java Programs    my programmed compiled but failed to run with error  Could not find or load main class  After all the possible solutions over SOF nothing worked   I realized may b space causing me this issue   Surprisingly removal of folder name space char  Java Programs  -   JavaPrograms    my program executed successfully  Hope it helps

User · Answer

When the Main class is inside a package then you need to run it as follows     java  lt packageName gt   lt MainClassName gt    In your case you should run the program as follows     java org tij exercises HelloWorld

[java] "Could not find or load main class" Error while running java program using cmd prompt

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