为什么下面的简单 Java 代码块（打印 Hello World ）会引发编译错误？

Question

This is a simple Java program within a Java file named HelloWorld.java. Apart from the HelloWorld class that has the main method, there is another class named generic that instantiates one HelloWorld object and calls a public method defined within the HelloWorld class. Why does this program not compile ?.

Error says - [Syntax error on token "dummyMethod()", identifier expected after this token.]

public class HelloWorld {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
            System.out.println("Hello World !");

    }

    public HelloWorld() 
    {
        System.out.println("Hello World Constructor !");
    }

    public void dummyMethod()
    {
        System.out.println("This method does nothing...");

    }

}

class generic 
{
       HelloWorld hw_object = new HelloWorld();
       hw_object.dummyMethod();
}

Answer 1

You can't just put code inside a class. It needs to be in a method.

public class HelloWorld {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println("Hello World !");

        HelloWorld hw_object = new HelloWorld();
        hw_object.dummyMethod();
    }

    public HelloWorld() 
    {
        System.out.println("Hello World Constructor !");
    }

    public void dummyMethod()
    {
        System.out.println("This method does nothing...");
    }
}