Run from cmd a Java program that contains other packages

[Ioanna Katsanou]

Hello,

this is my first post to Coderanch !!

I am having a problem. I know how to compile and run Java programs from cmd successfully.
I am having a problem with the following:
I have two folders named : packagea and packageb
In package a I have a class named ClassA.java

package packagea;
public class ClassA {
}

and in packageb I have a class named ClassB.java

package packageb;

public class ClassB {
public static void main(String[] args) {

System.out.println("Got it");
}
}

I compiled ClassA with success and I compiled and run ClassB successfully from the command line.
When I alter ClassB like bellow:

package packageb;
import packagea.ClassA;
public class ClassB {
public static void main(String[] args) {
ClassA a;
System.out.println("Got it");
}
}

It cannot run. It throughs a class not found exception
What am I doing wrong???

[Knute Snortum]

What's the exact and entire error message?  What directory are you running from?  When I'm in the directory that contains packagea and packageb and execute
java packageb.ClassB
I get "Got it".  I believe this is because the CLASSPATH contains "." by default.  Maybe try:
java -cp . packageb.ClassB

[Campbell Ritchie]

Are you setting the CLASSPATH at all? I have never needed a CLASSPATH for such a simple application. Please confirm that the first package is in a folder called packageA and similarly for packageB. Navigate to a folder where the dir/cpls command shows both packages in its output, i.e. the parent folder for both packages. Now try compiling and executing it with
javac packageA/ClassA.java
javac packageB/ClassB.java
java packageB.ClassB

...and welcome to the Ranch

[Edit;]Not cp; that was a mistake. Use dir on Windows® and ls on *nix.

[Ioanna Katsanou]

Hello,

this is the detailed case:

I have a folder named "folder", which is located on the dekstop of my computer.
So the full path would be C:\Users\Ioanna\Desktop\folder.

Inside that folder I have created a folder which I named packageA. so the path to this would be C:\Users\Ioanna\Desktop\folder\packageA.
I also have another folder which I named packageB. so the path to this would be C:\Users\Ioanna\Desktop\folder\packageB.

Inside packageA, I have a .java file, called ClassA.java. Which is the following:

package packageA;

public class ClassA{

}

Inside packageB, I have a .java file, calles ClassB.java:

package packageB;
import packageA.ClassA;

public class ClassB {

	public static void main(String[] args) {
		ClassA a;
		System.out.println("Got it");
	}
}

In Windows cmd I type:

C:\Users\Ioanna\Desktop\folder>javac C:\Users\User\Desktop\penny\packageA\ClassA.java

and it compiles and creates the ClassA.class successfully.

Then I type:

C:\Users\Ioanna\Desktop\folder>javac C:\Users\User\Desktop\penny\packageB\ClassB.java

and it compiles and creates the ClassA.class successfully.

(I could also do

C:\Users\Ioanna\Desktop\folder\packageA>javac ClassA.java

and the same thing for ClassB)


Then, I type

C:\Users\Ioanna\Desktop\folder>java -cp C:\Users\User\Desktop\penny\packageB\ ClassB

and I get:
Error: could not find or load main ClassB.

When I modify the code of ClassB to this:

//package packageB;
import packageA.ClassA;

public class ClassB {

	public static void main(String[] args) {
		ClassA a;
		System.out.println("Got it");
	}
}

and recompile ClassB and run it, I get
"Got it"

[Dave Tolls]

That last classpath is wrong.
You don't need it at all, since the root for your classes is "folder" and the java command defaults to '.' if you don't give a classpath, which in this case would be correct.

[Ioanna Katsanou]

OK, that seems to work !!! thank you !!


I returned the classB as I had it before , compiled it and typed:

C:\Users\Ioanna\Desktop\folder>java package.ClassB

and it ran !!