I am new to Java, and am currently studying how to create packages with related classes in Eclipse.

If I create one class (example: Circle) defining the methods ( writing()) I want to use, and another class using those methods, do I have to include a reference to an instance of that class? Here is a code example of what I mean:

public class Circle{ 
    double r; 
    void wirte() { 
         Syste.out.println("Hello");
    }  

and in the other class:

public class Circle2{ 
     public static void main(String[] args) { 
          write(); 
  }} 

Would that work? Or do I always have to follow that format: classinstance.methodname()?

UPDATE

I did not know I can do something like this

public class GUI(){
//do something
}

public static void main(String[] args){
   new GUI();
}

This code block worked for me --- thank you for pointing it out.

---------

So my IDE flagged an error at this line in main (from my main class Tic_Tac_Toe)

public static void main(String[] args) {

        ColRowLists ttt = new ColRowLists();
        char[][] board = new char[3][3];
        System.out.println("Welcome to Tic Tac Toe");
        userInput(board);

        System.out.println("show me your list" + ttt.winOrLose()); //"'winOrLose(java.util.List, java.util.List, java.util.List, java.util.List, java.util.List, java.util.List, java.util.List, ...)' in 'ThirtyMinutes.ColRowLists' cannot be applied to '()'"


    }

The winOrLose method in question lies in another class ColRowList: https://github.com/morry239/TTT_experiements/blob/master/src/ThirtyMinutes/Tic_Tac_Toe.java

I tried to do something like this, but it did not work obviously:

System.out.println("show me your list" + ttt.winOrLose(List topRow, List midRow, List botRow, List leftCol, List midCol, List rightCol, List diagonal1, List diagonal2);

Could anyone kindly point me in the right direction? My main class is here FYI.