Printing message on Console without using main() method

Question

I was asked this question in an interview.

How to print message on console without using main() method?

Answer 1

class MainMethodNot
{
    static
    {
        System.out.println("Hello World");
        System.exit(0);

    }
}

Because the static initializer block is executed when the class is first loaded, we can print out “Hello World” without writing a main method. The execution is stopped using “System.exit()” command. So, we prevent “main method not found” error. It's quite a tricky question

Answer 2

public class Foo {
    static {
         System.out.println("Message");
         System.exit(0);
    } 
}

The System.exit(0) exits program before the jvm starts to look for main()

_{(Note: This works only with java 6. Even if it compiles with JDK 7's javac it cannot be run with its java, because it expects a main(String[]) method.)}

Answer 3

It was possible till java 6 to use System.out.println(); without main(). From java 7 onwards, it is not possible to do it with static block. It will still ask for main method in main class.

Answer 4

Actually it doesn't work in the latest update of java 8. You can call it a bug fix according to them, but as far as I believe on my current knowledge this can't be called as a bug fix because it also lead to few conceptual changes too in java programming.

Answer 5

Yes, you can print a message to console without using main().

Create a test with JUnit and execute it:

@Test
public printTest()   {
   System.out.println("myprint");
}

Answer 6

If you don't want to use static block too, it can be done following way

public class NoMain {

    private static final int STATUS = getStatus();

    private static int getStatus() {
        System.out.println("Hello World!!");
        System.exit(0);
        return 0;
    }

}

However, please note that this is for Java 6 version. Its not working in Java 7 which is said to be supported in Java 8. I tried with JDK 1.8.0_77-b03, which is still not working