I know this question has been asked a lot, but I have tried a few suggestions and am still getting this error.
I am running the jar as follows:
java -jar MyJar-1.0.jar com.me.ldap.ActiveMain,
where my ActiveMain.java file looks like this:
package com.me.ldap;
public class ActiveMain {
public static void main(String[] args) throws Exception {
...
}
}
I have also tried simply java -jar MyJar-1.0.jar with the same Error: Could not find or load main class error. I've also looked into the class path option but I don't think that applies.
I am creating it in Intellij as a Maven project. Maven > Lifecycle > package.
In order for:
java -jar myfile.jar
to work, there must be a manifest file in the jar file that points to a main class.
In order for you to specify the main class on the command line, you need to specify a classpath, not a jar file. Like:
java -cp myfile.jar com.me.ldap.ActiveMain
You are conflating these two things. Either create a manifest that specifies your main class and use the -jar switch, or simply use the -cp switch and specify your main class on the command line.
Have you tried removing the signature files? I have seen this error pop up sometimes when due to signature files as documented in "Invalid signature file" when attempting to run a .jar and Generated JAR throws ClassNotFoundException for main class is also in the similar vein.
Related
My java class files run in Eclipse but not in command line. I have tried all possible solutions. My code has the following structure:
Client_1/src/filedownload/Client.java
RMI_interface/src/filedownload/Hello.java
The Client.java file is dependent on Hello.java. filedownload is the name of package.
When I compile using the following command, it works.
javac RMI_interface/src/filedownload/Hello.java Client_1/src/filedownload/Client.java
But when I execute the class file in the Client_1/src folder using following command, it does not work.
java filedownload.Client
The error displayed is
Could not find or load main class
I have tried many posts on stackoverflow but I am unable to solve it. I am using ubuntu.
The code structure is
package filedownload;
import ....
public class Client implements Hello, Runnable{
...other functions.....
public static void main(String args[])throws Exception{
}
}
Does your Client class have the main() method ? Where are the .class files after compilation (that is, what's the current directory you're executing the compile from) ? What's the current directory when you try to execute ? What's the classpath when you try to execute ?
Without all that info, there's little chance of anyone being able to get you going (but for the obvious advice of just setting up eclipse and doing everything from within eclipse - letting eclipse take care of all the nitty gritty detail).
(And the questions themselves suggest various possible points of failure in your scenario so look at it.)
All your steps seems to be correct. You didn't share the Client.java code which has main method.
Make sure you follow this main method syntax:
public static void main(String[] args){
...
}
E.g. if you write main without args, it can't be found.
You need to put your classes in a separate folder, separated from your sources.
javac -d bin RMI_interface/src/filedownload/Hello.java Client_1/src/filedownload/Client.java
(folder 'bin' must exist already)
And inside folder 'bin' execute command:
java filedownload.Client
I am trying to compile and run some java files I have made in Eclipse. The full path to the .java file is C:\Users\MYNAME\Documents\Java\Introduction\src\tests\Test.java. tests is the package I created in Eclipse and src is a folder that Eclipse made under Introduction (which is the project name).
In my environment variables, I have the following relevant variable:
JAVA_HOME C:\Program Files (x86)\Java\jdk1.7.0_40\bin
Under system variables I have the following:
CLASSPATH %JAVA_HOME%
I go to my cmd and cd into the tests directory (cd C:\Users\MYNAME\Documents\Java\Introduction\src\tests). Then I compile using javac Test.java. This seems to work as I then have a Test.class file under the same directory. Now I want to run the file, I type java Test and I get the error, "could not find or load main class". I've tried a variety of things including appending .class and .java to the end but I keep getting the error. I looked at some answers and docs and I managed to get it to work if I cd into:
cd C:\Users\MYNAME\Documents\Java\Introduction\src (i.e, get out of the package)
and then run:
java -cp . tests.Test
So that seems to temporarily set the class path to the current directory, and run Test from the package tests. However, I want to simply be able to type java Test. I know it's possible as I used to be able to do it, but now for some reason I cannot (I must have changed something along the way...).
Any help is appreciated.
However, I want to simply be able to type java Test
That will only work if Test is in the default package - it's as simple as that. You need to pass the java executable the fully-qualified name of the class you want to launch. There's no way round that.
Of course, you could create your own launcher which looks in the current directory for class files, finds out the fully-qualified name of the classes within those files, and launches java providing the full name and probably specifying an appropriate classpath... but that seems like a lot of hassle compared with just including the package name in the command.
You could be making the same mistake I made. So, try the following.
Here is my code for your reference.
class A{
public static void main(String args[]) {
System.out.println("Hello world");
}
}
Once you saved this as "C:\JavaStudy\ClassA.java", try the following.
c:\JavaStudy>javac ClassA.java
c:\JavaStudy>java A.class
Error: Could not find or load main class A.class
c:\JavaStudy>java A
Hello world
c:\JavaStudy>
Note: You don't need to use " java.exe -cp . " if you have class file in the same directory from where you are executing.
Java and Gradle beginner's question.
I made a project directory for java and gradle test:
The directory hierarchy :
HelloWorld.java:
package foo.bar;
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, world");
}
}
build.gradle:
apply plugin:'java'
Then,gradle build this project and generated what i need.
As you see above, my problem is why doesn't this execute correctly? Even through I cd to .class path.
======================================================================
While, if I remove package foo.bar; in HelloWorld.java, and repeat gradle commands and execute at he.bak directory then the error remained the same.
But when I cd to the directory where HelloWorld.java placed. everything goes OK！Why? something related with CLASSPATH environment variables or other causes?
////////////////////////////////////////////////////////////////////
UPDATE
////////////////////////////////////////////////////////////////////
Thought you guys' warm replies, I know that I should combine the CLASSPATH and the period-separated executable .class file to figure out what's going on when executing java class file.
I experiment my thought resulting in 2 point to this question:
The -cp option path parameter A/B plus the executable file c.d.e.class finally form the A/B/c.d.e.class full path where the class is actually located.
If I specify the package in source code file with package d,I must split the full path in the form of java -cp A/B/c/d e.class. split in other ways all will result in errors.
something I am not sure here is :
When I specify my package path in my source code file, It determined the only classpath when executing corresponding executable, right?
If it is the truth, How does a project with lots of package and sources files work?
What's the root principle?
When in build/classes/main try java foo.bar.HelloWorld instead of java HelloWorld
The reason you need to specify foo.bar.HelloWorld is because you specified package foo.bar;. This tells java that the class should be in foo/bar/HelloWorld and the fully qualified name for HelloWorld is foo.bar.HelloWorld. If you want to execute the class from a different working directory however, you can specify the classpath explicitly using the -cp option, e.g., java -cp c:\myproject\build\classes\main foo.bar.HelloWorld.
By the way, the classpath default is the current working directory (i.e., .) but java -cp c:\myproject\build\classes\main foo.bar.HelloWorld will NOT have the classpath set to the current working directory if it is explicitly set using the -cp option. If you want to include the current working directory but explicitly set it, or even add more directories, you can chain them using semicolons like this: java -cp .;c:\myproject\build\classes\main foo.bar.HelloWorld. So this will include both the current working directory and the directory I specified.
I have written two simple Java classes (one of them containing "main()", and the other called by "main()").
Class #1 (containing "main()"):
package daniel347x.outerjar;
import daniel347x.innerjar.Funky;
public class App
{
public static void main( String[] args )
{
Funky.foo();
}
}
Class #2 (called by "main()"):
package daniel347x.innerjar;
public class Funky
{
public static void foo()
{
System.out.println( "Funky!" );
}
}
The above classes appear in different project root folders, and use Maven as the build system (each project has its own POM). The pom.xml file for the main project includes the proper entry to add daniel347x.outerjar.App as the main class, and it properly includes the dependency on daniel347x.innerjar. Both projects build successfully into JAR files.
I use NetBeans to wrap these as Maven projects (in fact, I used NetBeans to create both projects). When I run the main project from within NetBeans, it runs successfully and I see Funky! as the output.
However, when I attempt to run the main class straight from the Windows command line (cmd.exe), passing the JAR file containing Funky on the command line's classpath, as such:
java -classpath "P:\_Dan\work\JavaProjects\JarFuckup\innerjar\target\innerjar-1.0-SNAPSHOT.jar" -jar "P:\_Dan\work\JavaProjects\JarFuckup\outerjar\target\outerjar-1.0-SNAPSHOT.jar"
... I receive the dreaded NoClassDefFoundError:
Exception in thread "main" java.lang.NoClassDefFoundError: daniel347x/innerjar/Funky
at daniel347x.outerjar.App.main(App.java:7)
I have carefully confirmed that, inside the innerjar JAR file noted above containing Funky, that the path structure is daniel347x\innerjar and that inside the innerjar folder is the Funky.class file - and this file looks correct within a HEX editor where I can see the ASCII strings representing the name of the class.
The fact that the class can't be found defies my understanding of Java, which I thought allows you to pass JAR files as a -classpath parameter and it will be able to find classes inside those JAR files.
This very basic point has me flummoxed - an answer that explains what I am doing wrong would be greatly appreciated.
The classpath is ignored when using the -jar option. A way to run your app would be java -classpath "P:\_Dan\work\JavaProjects\JarFuckup\innerjar\target\innerjar-1.0-SNAPSHOT.jar";"P:\_Dan\work\JavaProjects\JarFuckup\outerjar\target\outerjar-1.0-SNAPSHOT.jar" daniel347x.outerjar.App
Perhaps a better approach would be to add a manifest file to the Jar that specifies the class path of the dependent Jars by relative paths. Then..
java -jar "P:\_Dan\...\outerjar-1.0-SNAPSHOT.jar"
..should do it.
Double clicking the main Jar will also launch it. That is mostly useful for GUIs.
How can I create the class file and jar file for this coding, when I compile this program its not working because there is no main function in the program. And also I am trying in command prompt but I don't know how to set the classpath? please help me
My Coding is here
public class NewLogFields implements ILogNotify
{
public void onLog(Level level, String comment, IMediaStream stream, String category,String event, int status, String context) {
if (category.equals(WMSLoggerIDs.CAT_session) && event.equals(WMSLoggerIDs.EVT_destroy))
{
Long csBytes = (Long)WMSLoggerFactory.getGlobalLogValue(WMSLogger IDs.FD_cs_bytes);
Long scBytes = (Long)WMSLoggerFactory.getGlobalLogValue(WMSLogger IDs.FD_sc_bytes);
System.out.println("disconnect: csBytes:"+csBytes+" scBytes:"+scBytes);
}
}
}
Once you compiled the coding in wowza media Serever the jar file is automatically created in the library folder,see your Installation Library folder.Still you have problem Gothrough this link Wowza Quick Guide
What do you want to do?
Create a class and an jar file out of this Java code so that you can use this in another Java program?
Then you have to compile it:
java NewLogFields.java
Looks like you are unable to compile it at all. This could be because the interface ILogNotify (or the jar that contains this) is not in the classpath.
You can include the path/jar containing this interface in the classpath by using:
javac -cp .;path_to_jar_or_class NewLogFields.java
where path_to_jar_or_class is the path to the folder or jar file that contains ILogNotify.
For example, this may be something like ./logNotify.jar or ./log/
You can set use switch -cp or -classpath with javac command.
for example javac -cp path and name of jat file or class file yourjavafile.java
create the class file using the compiler: javac NewLogFileds.java
create the jar file using the jar command: jar cvf stuff.jar NewLogFileds.class
You are correct that the program needs a main() function in order to run.
add:
public static void main(String args[]) {
// code here
}
With that you could run the code with or without the jar:
java NewLogFields
or
java -cp stuff.jar NewLogFields
There are ways of creating a MANIFEST file that tells java which class to run from the jar making the last line more simple.
The link that you provided tells you how to do it:
Compile your class in the normal way.
Create a JAR file containing your class in the normal way.
Copy the JAR file into the wonza installation's lib as described in the javadoc.
Edit the startup script to add the -Dcom.wowza.wms.logging.LogNotify=... option to JAVA_OPTS ... as described in the javadoc.
The "full-path-to-your-ILogNotify-class" is actually supposed to be the fully qualified class name of your class; it is obvious from the examples.
Edit WowzaMediaServerPro-Service.conf and log4j.properties as described in the javadoc.
Restart the server.
If you put your JAR file in the directory like the instructions tell you to, you won't need to modify the classpath by changing -cp argument.
Your class doesn't need a main method because it is not a free-standing application. Rather, it is a "plugin" class that gets dynamically loaded and instantiated by the Wowza core as required. The "-D..." option and the config file change tell the Wonza core which class to try to load.