Could not find the main class program will exit

Question

I made an executable jar with the command prompt in Windows 7 using the  jar cvfm MyJarName jar manifest txt   class   which created the  jar file  But when I attempt to open it  I get a pop-up window that says   Could not find the main class   lt ClassName gt   Program will exit    Yet  when I use  java -jar jarName jar   in the command prompt  it works fine  What s the deal  I want to be able to just double-click it

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Tweaking MB s answer for windows  will get rid of the console window   start javaw -jar squirrel-sql jar

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I had this problem when I  upgraded  to Windows 7  which is 64-bit   My go to Java JRE is a 64-bit JVM   I had a 32-bit JRE on my machine for my browser  so I set up a system variable   JRE32 C  Program Files Java jre7   When I run     JRE32 bin java  -version   I get   java version  1 7 0 51  Java TM  SE Runtime Environment  build 1 7 0 51-b13  Java HotSpot TM  Client VM  build 24 51-b03  mixed mode  sharing    Which is a 32-bit JVM   It would say  Java HotSpot TM  64-Bit  otherwise   I edited the  squirrel-sql bat  file  REMarking out line 4 and adding line 5 as follows    4  rem set  IZPACK JAVA  JAVA HOME    5  set IZPACK JAVA  JRE32    And now everything works  fine and dandy

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If you are using JDK 1 6 or higher then you can override the manifest attribute via e flag of Jar tool   Read - Setting an Entry Point with the JAR Tool    Example   package pack   public class Test     public static void main String   args              System out println  Hello World              Compile and run Jar tool   c   gt jar cfe app jar pack Test pack Test class   Invoke app  c  gt java -jar app jar

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JAVA HOME variable must be set  to point to the prog files java version    bin open squirrel-sql bat file with some text editor and see if the JAVA HOME variable there is the same as the one in your enviroment variable change it if it doesn t match    and than run bat file again

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I was facing the same problem  What I did is I right clicked the project- properties and from  Select Binary Format  combo box  I selected JDK 6  Then I did clean and built and now when I click the Jar  It works just fine

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I got this issue in opening JMeter 4 0  I fixed as below   I have JRE 7 installed in Program Files  x86  folder and JDK 8 installed in Program files folder  So I just uninstalled JRE7 from machine  I just kept latest version of JDK  It fixed the problem

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Is Java installed on your computer   Is the path to its bin directory set properly  in other words if you type  java  from the command line do you get back a list of instructions or do you get something like  java is not recognized as a           You could try try running squirrel-sql jar from the command line  from the squirrel sql directory   using   java -jar squirrel-sql jar

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if you build the source files with lower version of Java  example Java1 5  and trying to run that program application with higher version of Java  example java 1 6  you will get this problem  for better explanation see this link  click here

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The Manifest text file must end with a new line or carriage return  The last line will not be parsed properly if it does not end with a new line or carriage return

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I tried to start SQUirrel 3 1  but I received a message stating   Could not find the main class Files Rational ClearQuest cqjni jar  I noticed that C  Program Files Rational ClearQuest cqjni jar is in my existing classpath as defined by the Windows environment variable  CLASSPATH     SQUirrel doesn t need my existing classpath  so I updated the SQUirrel bat file  squirrel-sql bat    REM SET SQUIRREL CP  TMP CP   CLASSPATH   SET SQUIRREL CP  TMP CP   It no longer appends my existing classpath to its classpath and runs fine

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Check out doing  this way  works on my machine    let the file be x java   compile the file javac x java jar cfe k jar x x class    k jar is jar file java -jar k jar

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Have you followed these instructions   http   www squirrelsql org  installation  If so  are you running the batch file or the shell script to run it

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Extract the jar and compare the contents of the manifest inside the jar with your external manifest txt  It is quite possible that you will locate the problem

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The classpath is the path that the system will follow when trying to find the classes that you re trying to run   In the batch file you re trying to execute it probably has a variable like CLASSPATH blah blah etc or a java command that looks similar to  java -classpath  c  directory lib squirrel-sql jar  com some squirrel package file   If you can find or add that classpath setting  make sure that it includes a path to the squirrel-sql jar and any other jar files that it may depend on separated by semicolons  or the root  lib directory that may be included with the installation    Basically you just need to tell java where to find the class files that you re trying to execute   Wikipedia has a more indepth discussion about classpath and can offer you more insight  http   en wikipedia org wiki Classpath  Java

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The  bat file does not seem to work   Just double-click on   squirrel-sql jar   or type   java -jar squirrel-sql jar   in the command-line

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Ha  I found what the problem was  I made my program using jdk1 7  but I had jre6 installed  I went and upgraded to jre7  and now it works fine     The  java -jar jarname jar   line was working in the command prompt because my java path was set to the jdk folder

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You can place    in classpath in environmental variables to overcome this problem

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I had the same issue with a different application  BI Publisher  because I installed a 32 bit version of this application on a 64 bit version of Windows   Java Virtual Machine Launcher - could not find the main class     The solution for my case was to tell BI Publisher where to find the x86 version of JRE

[java] Could not find the main class, program will exit

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