Interview Questions - Core Java

Can a class be declared as static?
We can not declare top level class as static, but only inner class can be declared static.
public class Test
    static class InnerClass
        public static void InnerMethod()
        { System.out.println("Static Inner Class!"); }
    public static void main(String args[])
//output: Static Inner Class!

When will you define a method as static?
When a method needs to be accessed even before the creation of the object of the class then we should declare the method as static.

What are the restriction imposed on a static method or a static block of code?
A static method should not refer to instance variables without creating an instance and cannot use "this" operator to refer the instance.

I want to print "Hello" even before main() is executed. How will you acheive that?
Print the statement inside a static block of code. Static blocks get executed when the class gets loaded into the memory and even before the creation of an object. Hence it will be executed before the main() method. And it will be executed only once.