title: Why a variable is declared static in java?
body: <p>I am following a book called "Big Java late objects" and right now I am studying GUI.
  The thing that I cannot understand why is in the following piece of code. Some of the field variables are declared "static" why?:</p>
  
  <pre><code>public class InvestmentFrame2 extends JFrame{
  
     private static final int FRAME_WIDTH = 450;
     private static final int FRAME_HEIGHT = 100;
  
     private static final double DEFAULT_RATE = 5;
     private static final double INITIAL_BALANCE = 1000;
  
     private JLabel rareLabel;
     private JTextField rateField;
     private JButton button;
     private JLabel resultLabel;
     private double balance;
  </code></pre>
  
  <p>}</p>