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Re: A question about some long java code that has getters/setters

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On 7/23/2011 12:02 PM, lewbloch wrote:
> Chad wrote:
>> The following code, which is taken from one of my school books,
>> displays 4 different boxes inside a gui [sic]
>>
>> import java.awt.*;
>> import javax.swing.*;
>>
>> public class TestMessagePanel extends JFrame {
>>
>>      public TestMessagePanel() {
>>          MessagePanel messagePanel1 = new MessagePanel("Top Left");
>>          MessagePanel messagePanel2 = new MessagePanel("Top Right");
>>          MessagePanel messagePanel3 = new MessagePanel("Bottom Left");
>>          MessagePanel messagePanel4 = new MessagePanel("Bottom Right");
>>          messagePanel1.setBackground(Color.RED);
>>          messagePanel2.setBackground(Color.CYAN);
>>          messagePanel3.setBackground(Color.GREEN);
>>          messagePanel4.setBackground(Color.WHITE);
>>          messagePanel1.setCentered(true);
>>
>>          setLayout(new GridLayout(2, 2));
>>          add(messagePanel1);
>>          add(messagePanel2);
>>          add(messagePanel3);
>>          add(messagePanel4);
>>      }
>>
>>      public static void main(String[] args) {
>>          TestMessagePanel frame = new TestMessagePanel();
>>          frame.setSize(300, 200);
>>          frame.setTitle("TestMessagePanel");
>>          frame.setLocationRelativeTo(null);
>>          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
>>          frame.setVisible(true);
>>
>>      }//end main()
>>
>> }
>>
>> class MessagePanel extends JPanel {
>>
>>      private String message = "Nope";
>>      private int xCoordinate = 20;
>>      private int yCoordinate = 20;
>>      private int interval = 10;
>>      private boolean centered;
>>
>>      public MessagePanel() {
>>      }
>>
>>      public MessagePanel(String message) {
>>          this.message = message;
>>      }
>>
>>      public String getMessage() {
>>          return message;
>>      }
>>
>>      public void setMessage(String message) {
>>          this.message = message;
>>          repaint();
>>      }
>>
>>      public int getXCoordinate() {
>>          return xCoordinate;
>>      }
>>
>>      public void setXCoordinate(int x) {
>>          this.xCoordinate = x;
>>          repaint();
>>      }
>>
>>      public int getYCoordinate() {
>>          return yCoordinate;
>>      }
>>
>>      public void setYCoordinate(int y) {
>>          this.xCoordinate = y;
>>          repaint();
>>      }
>>
>>      public boolean isCentered() {
>>          return centered;
>>      }
>>
>>      public void setCentered(boolean centered) {
>>          this.centered = centered;
>>          repaint();
>>      }
>>
>>      public int getInterval() {
>>          return interval;
>>      }
>>
>>      public void setInterval(int interval) {
>>          this.interval = interval;
>>          repaint();
>>      }
>>
>>      protected void paintComponent(Graphics g) {
>>          super.paintComponent(g);
>>
>>          if (centered) {
>>              FontMetrics fm = g.getFontMetrics();
>>              int stringWidth = fm.stringWidth(message);
>>              int stringAscent = fm.getAscent();
>>              xCoordinate = getWidth() / 2 - stringWidth / 2;
>>              yCoordinate = getWidth() / 2 - stringAscent / 2;
>>          }
>>          g.drawString(message, xCoordinate, yCoordinate);
>>      }
>>
>>      public void MoveLeft() {
>>          xCoordinate -= interval;
>>          repaint();
>>      }
>>
>>      public void MoveRight() {
>>          xCoordinate += interval;
>>          repaint();
>>      }
>>
>>      public void moveUp() {
>>          yCoordinate -= interval;
>>          repaint();
>>      }
>>
>>      public void moveDown() {
>>          yCoordinate += interval;
>>          repaint();
>>      }
>>
>>      public Dimension getPreferredSize() {
>>          return new Dimension(200, 30);
>>      }
>>
>> }
>>
>> What I don't get is why the book defines stuff like getXCoordinate(),
>> getYCoordinate(), and getInterval() when it doesn't even use them in
>> this very long code example. I tried reading over the section in the
>> book, but the author gives no explanation on why he included a bunch
>> of unused getters/setters. On top of that, the code seems to work fine
>> when I comment out these methods.
>>
>> Ideas?
>
> The problem with this code is that it teaches the bad and bug-prone
> practice of creating GUI elements on the main thread instead of the
> EDT.  Don't use this book.  The author apparently didn't know what he
> was doing.
>
> It is standard practice to create accessors and mutators for class
> attributes.  There's nothing wrong with that.  The class is written as
> any good API writer (a.k.a. "programmer") should in that one respect.
> While you should not build features into a class on a remote chance of
> their use, if you have properties then you should provide the get/set
> methods for them quite nearly always.
>
> But you should never, never, never do GUI magic off the EDT!

Maybe the book is just not new.

It was common practice to initiate the Swing form from the
main thread for some years until people got aware of the
potential issue.

Arne

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A question about some long java code that has getters/setters Chad <cdalten@gmail.com> - 2011-07-22 16:12 -0700
  Re: A question about some long java code that has getters/setters Arne Vajhøj <arne@vajhoej.dk> - 2011-07-22 19:28 -0400
  Re: A question about some long java code that has getters/setters Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-07-22 23:31 +0000
  Re: A question about some long java code that has getters/setters markspace <-@.> - 2011-07-22 16:51 -0700
  Re: A question about some long java code that has getters/setters lewbloch <lewbloch@gmail.com> - 2011-07-23 09:02 -0700
    Re: A question about some long java code that has getters/setters blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-23 17:41 +0000
      Re: A question about some long java code that has getters/setters lewbloch <lewbloch@gmail.com> - 2011-07-23 11:42 -0700
      Re: A question about some long java code that has getters/setters Arne Vajhøj <arne@vajhoej.dk> - 2011-07-23 17:59 -0400
        Re: A question about some long java code that has getters/setters Steve Sobol <sjsobol@JustThe.net> - 2011-07-23 23:39 -0700
          Re: A question about some long java code that has getters/setters blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-25 19:44 +0000
          Re: A question about some long java code that has getters/setters lewbloch <lewbloch@gmail.com> - 2011-07-26 09:03 -0700
    Re: A question about some long java code that has getters/setters Arne Vajhøj <arne@vajhoej.dk> - 2011-07-23 19:26 -0400
      Re: A question about some long java code that has getters/setters lewbloch <lewbloch@gmail.com> - 2011-07-26 09:00 -0700
    Re: A question about some long java code that has getters/setters Patrick May <patrick@softwarematters.org> - 2011-07-25 16:27 -0400
      Re: A question about some long java code that has getters/setters markspace <-@.> - 2011-07-25 15:14 -0700
      Re: A question about some long java code that has getters/setters lewbloch <lewbloch@gmail.com> - 2011-07-25 15:56 -0700
        Re: A question about some long java code that has getters/setters Patricia Shanahan <pats@acm.org> - 2011-07-25 17:00 -0700
          Re: A question about some long java code that has getters/setters Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-07-25 21:17 -0400
      Re: A question about some long java code that has getters/setters markspace <-@.> - 2011-07-25 16:50 -0700
        Re: A question about some long java code that has getters/setters Gene Wirchenko <genew@ocis.net> - 2011-07-25 18:30 -0700
          Re: A question about some long java code that has getters/setters Patricia Shanahan <pats@acm.org> - 2011-07-25 18:41 -0700
          Re: A question about some long java code that has getters/setters lewbloch <lewbloch@gmail.com> - 2011-07-26 09:05 -0700
          Re: A question about some long java code that has getters/setters Gene Wirchenko <genew@ocis.net> - 2011-07-26 10:48 -0700
            Re: A question about some long java code that has getters/setters Gene Wirchenko <genew@ocis.net> - 2011-07-26 11:56 -0700
              Re: A question about some long java code that has getters/setters Patricia Shanahan <pats@acm.org> - 2011-07-26 13:34 -0700
                Re: A question about some long java code that has getters/setters lewbloch <lewbloch@gmail.com> - 2011-07-26 14:21 -0700
            Re: A question about some long java code that has getters/setters lewbloch <lewbloch@gmail.com> - 2011-07-26 14:20 -0700
        Re: A question about some long java code that has getters/setters Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-07-25 21:35 -0400
        Re: A question about some long java code that has getters/setters Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-07-26 06:59 -0300
    Re: A question about some long java code that has getters/setters Jukka Lahtinen <jtfjdehf@hotmail.com.invalid> - 2011-07-26 12:19 +0300
      Re: A question about some long java code that has getters/setters lewbloch <lewbloch@gmail.com> - 2011-07-26 09:08 -0700
        Re: A question about some long java code that has getters/setters Jukka Lahtinen <jtfjdehf@hotmail.com.invalid> - 2011-07-27 15:56 +0300
          Re: A question about some long java code that has getters/setters lewbloch <lewbloch@gmail.com> - 2011-07-27 14:14 -0700

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