Simple newbish error, public classes should be in its own file?

[voidflux]

Hello everyone, i'm new to java, and i'm using the java 1.4 sdk SE compiler. I just copied and pasted this books source code to make sure I didn't make any typo's and it still brings up this error when i compile:

C:\TEST>javac count.java
count.java:31: class CountInstances is public, should be declared in a file name
d CountInstances.java
public class CountInstances {
       ^
1 error

Here's the code, all its doing is using the constructor to count the number of instances i've created.

public class CountInstances {
      private static int numInstances = 0;
 
      protected static int getNumInstances() {
          return numInstances;
      }
 
      private static void addInstance() {
          numInstances++;
     }

     CountInstances() {
         CountInstances.addInstance();
     }

     public static void main(String[] arguments) {
         System.out.println("Starting with " +
             CountInstances.getNumInstances() + " instances");
         for (int  i = 0; i < 10; ++i)
            new CountInstances();
         System.out.println("Created " +
            CountInstances.getNumInstances() + " instances");
    }
 }

THanks!


By the way when I take out the modifer public the code compiles fine, but why do I have to take the keyword public off the class? And why does this book suck so bad?