[java] Calling another method java GUI

I'm trying to make a GUI, and I can accomplish it all in one method, but I would like to make the code simpler and make multiple methods. However, I can't get it to work. I am new to Java programming.

public class Main {     public static void main(String[] args) {         FirstWindow fw = new FirstWindow();          fw.setVisible(true);         fw.setSize(600,400);     } }  public class FirstWindow extends JFrame {      public FirstWindow() {         checkbox c = new checkbox();         c();     } }   public class checkbox extends JFrame {      public checkbox() {           //code     } } 

I'm not sure what you're trying to do, but here's something to consider: c(); won't do anything. c is an instance of the class checkbox and not a method to be called. So consider this:

public class FirstWindow extends JFrame {      public FirstWindow() {         checkbox c = new checkbox();         c.yourMethod(yourParameters); // call the method you made in checkbox     } }  public class checkbox extends JFrame {      public checkbox(yourParameters) {          // this is the constructor method used to initialize instance variables     }      public void yourMethod() // doesn't have to be void     {         // put your code here     } }