HTTP Proxy: My grogram runs even I put a wrong proxy host and port

Question

I'm new to network programming, so I just use System.setProperty() for easy. But I don't know why this piece of code runs with whatever proxy I set:
(I download a file and display in a in JTextArea, this is the ActionListener for 'Download' button)
     private class GetFileListener implements ActionListener
          public void actionPerformed(ActionEvent event)
               if (completeRadioButton.isSelected())
                   try
                        viewFileTextArea.setText("");
                    System.setProperty("http.proxyHost", "http://123.123.123.123");
                    System.setProperty("http.proxyPort", "123");
                    System.setProperty("proxySet", "true");
                       URL url = new URL(completeURLTextField.getText());
                       BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
                       String str;
                       while ((str = in.readLine()) != null)
                           viewFileTextArea.append(str + "\n");
                       in.close();
                   catch (MalformedURLException e)
                        viewFileTextArea.setText("URL not found!");
                   catch (IOException e)
     }Please help! Thank you very much!

Answer 1

This is the new version:
     private class GetFileListener implements ActionListener
          public void actionPerformed(ActionEvent event)
               if (completeRadioButton.isSelected())
                   try
                        viewFileTextArea.setText("");
                    SocketAddress addr = new InetSocketAddress("123.123.123.123", 123);
                    Proxy proxy = new Proxy(Proxy.Type.HTTP, addr);
                    URL url = new URL(completeURLTextField.getText());
                    URLConnection conn = url.openConnection(proxy);
                       BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
                       String str;
                       while ((str = in.readLine()) != null)
                           viewFileTextArea.append(str + "\n");
                       in.close();
                   catch (MalformedURLException e)
                        viewFileTextArea.setText("URL not found!");
                   catch (IOException e)
     }but it still runs regardless of what proxy host and port I set in InetSocketAddress. Did I wrongly use Proxy class in the code above?