Package compilation problem

Question

Hi,
I'm presently trying to learn packages in java. I have two example classes I want to compile to learn to use packages. One is Dice class and on is ThrowDice. ThrowDice uses Dice by creating two Dice objects. If i put them in the same directory and compile them without any package declaration they compile fine. If I put ThrowDice into the directory home/antlaw/java/Applications with "import Parsons.Dice" and Dice into home/antlaw/java/Applications/Parsons with package declaration "package Parsons" they compile and work fine. However, because I'm wanting to learn how to compile packages I've experimented a bit, and found that 1) if i declare ThrowDice as a package also of "Applications" (i.e. the directory it's in) by adding "package Applications" the two classes compiles but won't run (throws a load of exceptions) 2) if I create another directory "Apps" and move ThrowDice into this subdirectory (i.e. home/antlaw/java/Apps) and make the following package and import declaration changes to both Dice and ThrowDice classes
Dice = "package Applications.Parsons"
ThrowDice = "package Apps" and "import Applications.Parsons.Dice"
ThrowDice won't compile as it gives the following errors:
ThrowDice.java:2: cannot resolve symbol
symbol : class Dice
location: package Parsons
import Applications.Parsons.Dice;
^
ThrowDice.java:8: cannot resolve symbol
symbol : class Dice
location: class Apps.ThrowDice
Dice dice1 = new Dice();
^
ThrowDice.java:8: cannot resolve symbol
symbol : class Dice
location: class Apps.ThrowDice
Dice dice1 = new Dice();
^
ThrowDice.java:9: cannot resolve symbol
symbol : class Dice
location: class Apps.ThrowDice
Dice dice2 = new Dice();
^
ThrowDice.java:9: cannot resolve symbol
symbol : class Dice
location: class Apps.ThrowDice
Dice dice2 = new Dice();
5 errors
indicating that it cannot find the Dice class.
In my home profile (I'm a linux user Suse 7.3) I've declared the classpath as follows:
export PATH=/home/antlaw/java:$PATH
I'm a bit "stumped" with what's wrong i.e. am i using packages incorrectly or is there something wrong with my classpath? Any help/advice would be gratefully received.
Cheers -- Tony.

Answer 1

Hi YATArchivist,
Firstly, thanks for the response - it's appreciated :-)
Secondly, I've put Dice (and it's package directory) into the following directory :
home/antlaw/java/Parsons
so now both package directories "Parsons" (with Dice class) and "Applications" (with ThrowDice class) are subdirectories of home/antlaw/java
Thirdly, I've tried all of your suggestions and there is a big improvement as both ThrowDice and Dice now compile (i don't know for sure what's improved it - but I took your advice and have now inserted "export CLASSPATH=/home/antlaw/java:$CLASSPATH" and i'm now thinking this was at fault).
However, I'm still not able to run ThrowDice (which calls Dice) as every time I do I get the following exception being thrown:
antlaw@linux:~/java> java ThrowDice
Exception in thread "main" java.lang.NoClassDefFoundError: ThrowDice
if I try out your various compile options I get the same "NoClassDefFoundError".
if I cd "Applications" and go into the same directory as ThrowDice and try and compile there I get:
Exception in thread "main" java.lang.NoClassDefFoundError: ThrowDice (wrong name: Applications/ThrowDice)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:486)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:111)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:248)
at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:297)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:286)
at java.lang.ClassLoader.loadClass(ClassLoader.java:253)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:313)
Here's a copy of both the java classes - in case there's something wrong here I'm not aware of
First Dice (home/antlaw/java/Parsons)
package Parsons;
public class Dice
     // class attribute
     private int dice_value;
     // public methods
     public void throwDice()
          double random_number = Math.random();
          random_number *= 6;
          random_number++;
          dice_value = (int) random_number;
     public int getDiceValue()
          return dice_value;
Here ThrowDice class
package Applications;
import Parsons.Dice;
public class ThrowDice
     public static void main(String args[])
          Dice dice1 = new Dice();
          Dice dice2 = new Dice();
          dice1.throwDice();
          dice2.throwDice();
          int dice1_score = dice1.getDiceValue();
          int dice2_score = dice2.getDiceValue();
          int total_score = dice1_score + dice2_score;
          System.out.println("The first dice shows " + dice1_score);
          System.out.println("The second dice shows " + dice2_score);
          System.out.println("Your total score is " + total_score);
Any ideas why this is happening? - thanks for your help so far too.
Cheers -- Tony.