Error running code examples from Training Video

Question

I am currently learning Java and I am using a Java Training series from Sun. There are several code examples that I am having problems running. I am 99.9% sure that my code is correct. That is the code that I have followed along and written.
Here is an example of code that I am trying to run. ( I am on OS X 10.5 BTW )
public class Person
     public int ageYears = 32;
     public void calculateAge()
          int ageDays = ageYears * 365;
          long ageSeconds = ageYears * 365 * 24L * 60 *60;
          long ageMinutes = ageSeconds / 60;
          long ageMilliseconds = ageSeconds * 1000;
          System.out.println("You are " + ageDays +  " days old.");
          System.out.println("You are " + ageSeconds + " seconds old.");
          System.out.println("You are " + ageMinutes + " minutes old.");
          System.out.println("You are " + ageMilliseconds + " milliseconds old.");
}After I create the file (which is named Person.java) I open the terminal and cd to the directory the file is in. In my terminal I first say
javac Person.java
I don't get any errors at all. Then I try to run the program like this.
java Person
When I try this I get the following error
Exception in thread "main" java.lang.NoSuchMethodError: main
I am not sure why I get this error. On the instruction video the instructors code seams to run just fine with out have a main function. The instructor is on Windows and I am not sure if that has anything to do with it or not?
Any thoughts or suggestions would be really helpful.

Answer 1

mswallace wrote:
I am currently learning Java and I am using a Java Training series from Sun. There are several code examples that I am having problems running. I am 99.9% sure that my code is correct. That is the code that I have followed along and written. Trust what the compiler and the JVM say to you.
I am not sure why I get this error. On the instruction video the instructors code seams to run just fine with out have a main function. The instructor is on Windows and I am not sure if that has anything to do with it or not?
Any thoughts or suggestions would be really helpful.So, as the error is asking you, where is the main method that every runnable program must have? This has nothing to do with windows and everything to do with all programs needing a main method to run (even applets where the main method is I believe within the Applet class code).