Java ACM JTF Package

Question

I have a doubt in the below piece of code. I wanted to know why does the code compile and run correctly even though main method is not present?

import acm.program.*;  

public class HelloConsole extends ConsoleProgram {  

   public void run() {  
      println("hello, world");  
   }    
}

Thanks.

Answer 1

This is by design of the ACM program classes. See the javadocs :

The conventional pattern of use associated with the acm.program package moves students away from the imperative style of public static void maininto a more pedagogically defensible framework in which students are always working in the context of an object.

In this case you override the init/run methods as opposed to writing a main method.

Answer 2

因为consoleprogram扩展了包含主方法的类程序。