why public keyword is necessory here?

[vianyrajnish rajnish]

hi all,


This is a simple java program -----

public class HelloWorldApp
{
public static void main(String arg[])
{
System.out.println("Hello World!");
}
}

here why do i declare -- public class HelloWorldApp -- for the class .?
if i remove (public) this i do get error..why is this?


can anyone please answer?




-- vinay rajnish

[Maurizio Nagni]

Generaly it is not an error to set "default" the class, but the error appears if you try to run it throught the "java HelloWorldApp" command; in this case the JVM cannot access the main method (because the class is not public).

To test that it just try to modify your HelloWorldApp file as

  
 public class HelloWorldApp {
   public static void main(String arg[]) {
     System.out.println("Hello World!");
     Test.main(new String[]{"ciao", "USER"});
   }
 } 
 
class Test {    
    public static void main(String[] args) {
        for (String str : args) {
            System.out.print(str);   
        }
    }    
}  

Note that in this case the code will give you an error if you define public the Test class because as defined in the Java syntax one file can contain one public class with a public static void main(String[] args) method.

Ciao

[asha ganapathy]

I think the keyword "public" is used so that other classes in the same package or in the different package can use this class.
If you dont declare HelloWorldApp class as public it means its using a default access(you can use this class only in the current package, hence even if you dont use public keyword for HelloWorldApp there should not be any compiler error.

[vianyrajnish rajnish]

hi all,

thanks for helping .... all of you are correct

thanks for helping with clearing the concepts..

vinay rajnish