running java program out of workspace

[Alex George]

I wrote a small java program in my eclipse workspace.

package com.mypackage;

public class HelloWorld {

public static void main(String[] args) {
for (int i = 0; i < 3; i++) {
System.out.println("Hello, world!");
}
}

}

I am able to compile and run this within eclipse.

Now I open the command window and compile this

C:\Projects\workspace\com\mypackage>javac HelloWorld.java

and it compiled

Now I am trying to run it

C:\Projects\workspace\com\mypackage>java HelloWorld
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld (wrong name: com/mypackage/HelloWorld)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)


this is happening because I have
package com.mypackage;

in the program.

If I delete the line
package com.mypackage;

I am able to compile and run this.

How can I run this without deleting the line
package com.mypackage;
from the program?

[Henry Wong]

C:\Projects\workspace\com\mypackage>javac HelloWorld.java

and it compiled

Try this instead....

C:\Projects\workspace>javac com\mypackage\HelloWorld.java

Now I am trying to run it

C:\Projects\workspace\com\mypackage>java HelloWorld
Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorld (wrong name: com/mypackage/HelloWorld)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)

Try this instead....

C:\Projects\workspace>java com.mypackage.HelloWorld



Note: Moving this to JiG (Beginner)

Henry

[Alex George]

Doesn't seem to be working.

C:\Projects\workspace>java com.myPackage.HelloWorld
Exception in thread "main" java.lang.NoClassDefFoundError: com/myPackage/HelloWorld

[kannan vinayagam Duraiswamy]

try by setting classpath

java -classpath <path for the class file> file name

java -classpath C:\Projects\workspace\com\myPackage\HelloWorld HelloWorld

[Campbell Ritchie]

One possibility:

You may have Eclipse configured to keep source and .class files in different directories. Beware of using IDEs as a beginner; you can spend longer learning about the IDE than about Java.

Copy and paste the HelloWorld.class file into another folder somewhere so it is inside a "mypackage" folder inside a "com" folder.

Then, as Henry said earlier, if you have

C:\---java---com---mypackage---HelloWorld.class

you can try:-

C:\someFolderOrOther> cd C:\java
C:\ java java com.mypackage.HelloWorld

It does take some time to get used to calling classes with a package name.

Another possibility:
If you have mypackage in the source and invoke it with myPackage the capital P will stop the java tool finding the correct location. Remember Java is CaSe-SeNsItIvE.

I don't think setting a classpath will help.

[salvin francis]

If I delete the line
package com.mypackage;

I am able to compile and run this.

As a added statement... by deleting the line, you are using the default package.

[salvin francis]

Campbell Ritchie wrote:Beware of using IDEs as a beginner; you can spend longer learning about the IDE than about Java.

I totally agree to this statement, IDE are the tools to build programs. Dont use them until you have mastered the basics of the language itself

[Alex George]

Actually I am not a beginner. I wrote a job in the folder
C:\Projects\workspace\Project1\src\com\fis\util using eclipse IDE.
This get compiled into the classes folder.
Now I want to run this job from the command line.
I couldn't do it. So I wrote a test program called HelloWorld to test it out.
So I need to run this job from command line.
How do I do that?

[Henry Wong]

Alex George wrote:Doesn't seem to be working.

C:\Projects\workspace>java com.myPackage.HelloWorld
Exception in thread "main" java.lang.NoClassDefFoundError: com/myPackage/HelloWorld

Java is case sensitive. From you previous posts, you said you package was in "com/mypackage" -- with a small p.

Henry

[Alex George]

I tried it. Didnt work.

[Campbell Ritchie]

Please post the directory structure you have, and show us which folder you are in trying to execute your app.

As an alternative: get a directory, empty it, copy and paste your HelloWorld class into it, and compile it with additional tags

javac -d . HelloWorld2.java

The dot tells the compiler to start looking in the "current directory" and -d means to create any directories (if they don't already exist).

Execute with

java com.mypackage.HelloWorld2

with all the spelling and CaPiTaLiSaTiOn correct.

[Nathan Heimdall]

Alex,

The way to run your program outside the Eclipse is to create a jar file.

You can use the Fat Jar Eclipse Plug-In and create a jar and then run the jar file from the command line by saying "java -jar filename.jar".

You could supply command line arguments cmd1 and cmd2 if you wanted by saying after the filename - "filename.jar" cmd1 cmd2.

Hope this helps,

[Alex George]

my HelloWorld.java file is in
C:\Projects\workspace\Project1\src\com\fis\util

my compiled file is in

C:\Projects\workspace\Project1\classes\com\fis\util

my classpath is
C:\Projects\workspace\Project1\classes\com\fis\util

[Henry Wong]

Alex George wrote:my HelloWorld.java file is in
C:\Projects\workspace\Project1\src\com\fis\util

my compiled file is in

C:\Projects\workspace\Project1\classes\com\fis\util

my classpath is
C:\Projects\workspace\Project1\classes\com\fis\util

Your HelloWord.java program is in the com.mypackage package. It needs to be in in a com\mypackage directory (from the classpath) to be compile and run properly. In this case, there is no classpath that you can set, that will get it to run correctly..

Henry

[Alex George]

Okay found it.
Go to the classes folder set classpath to classes folder
then
java com.fis.util.HelloWorld.

Thant worked.

[Campbell Ritchie]

Have you set a system classpath? You ought not to need a classpath for that sort of exercise. At least add a . to your system classpath.