java - Is there a point to this line of code? -

Until I came to someone's code on dreamincode, I had difficulty creating a sudoku grid using the readers But they did not really interpret it and I was thinking that any person here can explain me the class room. Thinking about this because the class is empty, even though the grid still works, so I'm confused. Thank you. Import java.awt. *; Import javax.swing *; Import javax.swing.border. *; Public Square Square JPNL (Public Final Ink CELL_COUNT = 9; Public Cells] Cells = New Cells [CELL_COUNT]; Public Square () {this.setLayout (New Grid Layout (3,3)); This.setBorder (New LineBorder Color (black, 2)); for (int i = 0; i & lt; CELL_COUNT; i ++) {cell [i] = new cell (); this.add (cells [i]);}} public Class cell JTextField {Private int number; public cell () {} public zero set number (int number) {this.number = number; this.setText ("1");} public int getNumber () {return number;}} }

I'm not a Java Pro, but I will try to explain it best I I can do.

  sections of the public category expanded by JPNL   
 class  sections  extension  JPanel , Which means that it is the child of  zpnil  class and behaves as one, therefore, as you add stuff to  JPanel , you can directly  sections < / Code> Accessories in the class (Label, textfield, etc.).  
  public class cell extends JTextField   
 Similarly, class  cell  extension  JTextField  Which means that behaving like objects in this class can be used on a textfield  setText ()  and can be added to  JPNEL .  
 Here are the creators of the class  class  
  public class (this.setLayout (new grid layout (3,3)); This.setBorder (new lineboard (Color Black, 2)); For (int i = 0; i & lt; cELL_COUNT; i ++) {cell [i] = new cell (); This.add (cells [i]); }}   
 In this manufacturer, the layout and threshold are first set. Then a loop is run, which instructs new objects of the  cell  class (which is basically  JTextField  s). And these cells are added to  sections  ( JPNL  class child).  
 Hope you understood it!  
 
 Edit:  
 In a comment, you have said that whenever you remove everything from the  cell  class, it still works This is because the class increases  JTextField  and it receives all the properties of its original class, just try to remove  Expand JTextField  it will not work.