J2SE: Taking screen snapshots in JAVA

As programmers many a times we need take snap shots of our screens. If we can take snap shot in java why use OS specific way to take a snap shot?
Here is a simple code example of taking snapshot in java (Either PNG format or JPEG format):

01 import java.awt.AWTException; 02 import java.awt.Dimension; 03 import java.awt.Rectangle; 04 import java.awt.Robot; 05 import java.awt.Toolkit; 06 import java.awt.image.RenderedImage; 07 import java.io.File; 08 import java.io.IOException; 09 import javax.imageio.ImageIO; 10  11 /** 12  * A Simple program that saves current screen snapshot. 13  * Supported formats png and jpg. 14  * Usage java ScreenSnapShot <<outputfilename>> 15  * 16  * @author Kumar Mettu 17  * @version 0.61 18  */ 19 public class ScreenSnapShot { 20  21     public static void main(String[] args) throws IOException,AWTException { 22  23         String saveFileName = "default.png"; 24         String saveFileFormat = "png"; 25  26         if (args.length > 0) 27             saveFileName = args[0]; 28  29         if (saveFileName.toLowerCase().endsWith(".png")) { 30             saveFileFormat = "png"; 31         } else if (saveFileName.toLowerCase().endsWith(".jpg") || 32                    saveFileName.toLowerCase().endsWith(".jpeg")) { 33             saveFileFormat = "jpg"; 34         } else { 35             System.err.println("Only png and jpg formats are supported."); 36             System.exit(1); 37         } 38  39         // get current sceen size for snapshot. 40         Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize(); 41         Rectangle screenRect = new Rectangle(screenSize); 42  43         // create current screen snapshot 44         RenderedImage image = (new Robot()).createScreenCapture(screenRect); 45  46         if (ImageIO.write(image, saveFileFormat, new File(saveFileName))) { 47             System.out.println("Screen snap shot is saved as :" + saveFileName); 48         } else { 49             System.out.println("Unable to save snap shot"); 50         } 51     } 52 }

This code requires J2SE1.4. There is no real use of this code unless you extend it to make use of it(like taking snapshots at fixed intervals etc...).

General: China to help Europe develop GPS rival

New Scientist reports China has joined a European effort to develop a new global satellite navigation system that would offer a more accurate civilian alternative to the Global Positioning System. The Galileo system will be precise to within a meter, while the civilian GPS service is accurate to around 10 meters. This development adds to the consternation of the U.S. military, which controls the GPS and currently enjoys the option of downgrading the civilian service during military conflicts.

Microsoft links with Motorola to launch mobile phone

Telegraph | Money | Microsoft links with Motorola to launch mobile phone: "Microsoft's bid to dominate the market for mobile phone operating systems will receive a boost today when the US software giant launches its first phone with a major handset maker."

Untold story:In a related product launch Steve Ballmer, Chief Executive Officer Microsoft Corp announced general availability of the Blue Screen of Death sized down for use in Motorola handset

J2SE: A nice tool to learn API differences

JDiff is a Javadoc doclet which generates an HTML report of all the packages, classes, constructors, methods, and fields which have been removed, added or changed in any way, including their documentation, when two APIs are compared. This is very useful for describing exactly what has changed between two releases of a product. Only the API (Application Programming Interface) of each version is compared. It does not compare what the source code does when executed.

Sample Reports:
Comparing J2SE1.4.0 and J2SE1.4.1
Comparing J2SE1.3.1 and J2SE1.4

J2ME: Turning your phone into web Server.

I wrote a simple midlet which turns my Phone into simple web server. To keep the code simple, I removed the additional GPS capabilities. Currently the web server listens to port 8000 and repsonds "Hello, I am Kumar Mettu's Phone. Thanks for Visiting" for all requests that are sent to this tiny web server. Note that this code is tested only on Motorola i88s with Nextel Total Connect Service.

Here is the code for the tiny web server:

001 import java.io.IOException; 002 import java.io.InputStream; 003 import java.io.PrintStream; 004  005 import javax.microedition.io.Connector; 006 import javax.microedition.io.StreamConnection; 007 import javax.microedition.io.StreamConnectionNotifier; 008 import javax.microedition.lcdui.Display; 009 import javax.microedition.midlet.MIDlet; 010  011 /** 012  * MIDlet working as simple personal WebServer. 013  * Currently this serves simple HTTP GET operation. 014  * 015  * @author Kumar Mettu 016  * @version 0.61 017  */ 018  019 public class WebServer extends MIDlet { 020  021     private Display display; 022  023     StreamConnectionNotifier scn = null; 024  025     /** 026      * Default constructor. 027      */ 028     public WebServer() { 029        display = Display.getDisplay(this); 030     } 031  032     /** 033      * This will be invoked when we start the MIDlet 034      */ 035     public void startApp() { 036         try { 037             scn =(StreamConnectionNotifier)Connector.open("serversocket://:8000"); 038             while (true) { 039                 StreamConnection sc = (StreamConnection)scn.acceptAndOpen(); 040  041                 // service the connection in a separate thread 042                 Connection c = new Connection(sc); 043                 c.start(); 044             } 045  046  047         } catch (IOException e) { 048             //Handle Exceptions any other way you like. 049             //No-op 050         } 051     } 052  053     /** 054      * Pause, discontinue .... 055      */ 056     public void pauseApp() { 057         try { 058             if (scn != null) 059                 scn.close(); 060         } catch(Exception e) { 061         } 062  063     } 064  065     /** 066      * Destroy. Cleanup everything. 067      */ 068     public void destroyApp(boolean unconditional) { 069         try { 070             if (scn != null) 071                 scn.close(); 072         } catch(Exception e) { 073         } 074     } 075  076     /** 077      * Thread to handle client request. 078      */ 079     class Connection extends Thread 080     { 081  082         public Connection(StreamConnection c) { 083             client = c; 084         } 085  086         /** 087          * Handles client request. 088          */ 089         public void run() { 090             InputStream s = null; 091             PrintStream out = null; 092             StringBuffer b = new StringBuffer(); 093             try { 094  095                 s = client.openInputStream(); 096  097                  //Ignore reading request to reduce the amount of data 098                  //transfered to Phone. 099                 /*int ch; 100                 while((ch = s.read()) != -1) { 101                     b.append((char) ch); 102                 } 103                 System.out.println(b.toString());*/ 104  105                 out = new PrintStream(client.openOutputStream()); 106                 String response = 107                              "<HTML>"+ 108                              "<HEAD>"+ 109                                 "<TITLE>Kumar's Location</TITLE>"+ 110                              "</HEAD>"+ 111                              "<BODY>Hello, I am Kumar Mettu's Phone. "+ 112                                      "Thanks for Visiting.</BODY>"+ 113                              "</HTML>"; 114                 out.println("HTTP/1.0 200 OK\n"); 115                 out.println(response); 116  117             } 118             catch (Throwable ioe) { 119                 //Handle Exceptions any other way you like. 120                 //No-op 121             } 122             finally { 123                 try { 124                     if (s != null) 125                         s.close(); 126                     if (out != null) 127                         out.close(); 128                     if (client != null) 129                         client.close(); 130                 } 131                 catch (IOException ioee) { 132           //Handle Exceptions any other way you like. 133           //No-op 134                 } 135             } 136         } 137  138         private StreamConnection client; 139     } 140  141 } 142

I know there is no business value for this web server. But hey turning phone into a web server and viewing it serve web pages to browser is fun :-)

J2ME: My new J2ME-GPS phone

Since my old phone is more than 2 years old, I bought a new Motorola i88s phone which has J2ME and GPS support.
I added some cool J2ME applications which will probably be blogging about in coming days.

Molecular Expressions: Science, Optics and You - Powers Of 10: Interactive Java Tutorial

Molecular Expressions: Science, Optics and You - Powers Of 10: Interactive Java Tutorial: "View the Milky Way at 10 million light years from the Earth. Then move through space towards the Earth in successive orders of magnitude until you reach a tall oak tree just outside the buildings of the National High Magnetic Field Laboratory in Tallahassee, Florida. After that, begin to move from the actual size of a leaf into a microscopic world that reveals leaf cell walls, the cell nucleus, chromatin, DNA and finally, into the subatomic universe of electrons and protons."