Questions In Java

Recently, I started learning Java programming language. I got a learning guide from the library. While I’m working on the example programs, I found that in all example the ‘public static void main’ comes before any method is being used or created. What does it mean?

 

While I’m working on a Java program, I got this compiler error: non-static variable count can not be referenced from a static context. Can anyone tell me What does it mean, why this error occurs, and How to fix this error?

I’m working on math.round() to round off this following code:

class round{
    public static void main(String args[]){
    double a = 123.13698;
    double roundOff = Math.round(a*100)/100;
    System.out.println(roundOff);
}
}

It returns 123, but I want it to be 123.14. It is required to be double for both input and output. Can anyone suggest an easy option?