CS 3291 (Java with Internet Applications):
Sample Programs

"Hello" examples

• Standalone program HelloWorld: HelloWorld.java.
• Applets:
  • HelloWeb: HelloWeb.java, HelloWeb.html.
  • HelloWeb2: HelloWeb2.java, HelloWeb2.html.
  • HelloWeb3: HelloWeb3.java, HelloWeb3.html.
  • HelloWeb4: HelloWeb4.java, HelloWeb4.html.
  • A page containing all four examples: AllHelloWeb.html.

Examples I used in teaching a previous Java course

• Examples of processing command-line arguments: Echo.java. Sum.java.
• Simple class example: NamedArray.java.
• Simulation-style example: RegisteredVehicleTest.java.
• Sorted linked list: OrderedIntList.java.
• Cloning, wrong and right ways: Clones.java.
• Nested classes: Nest1.java, Nest2.java, Nest3.java, Nest4.java.
• Use of core classes for parsing and formatting:
  • java.util.StringTokenizer: TestTokenizer.java.
  • java.text.NumberFormat: TestNumberFormat.java.
  • java.util.Date: TestDate.java.
  • java.util.Calendar, java.text.DateFormat: TestCal.java.
• Use of other core classes:
  • java.text.DecimalFormat: TestDecimalFormat.java (simpler scheme for formatting numeric output than the one in TestNumberFormat above).
  • System properties table (analogous to environment variables in some other languages/systems): ShowSystemProps.java. ShowSystemProps.OUT show sample output on one of the CISE Unix machines; compare to output on your system.
• Use of Java input/output and related classes:
  • TestFile.java demonstrates use of File class to get information about a file (or directory).
  • TestDataStreams.java demonstrates use of Data* classes to read/write data in binary format, ByteArray* classes to use a byte array as a source/destination, and connecting streams in sequence.
  • TestStreamTokenizer.java demonstrates use of StreamTokenizer and PrintWriter classes to parse input and print results.
  • TestFilters.java demonstrates user-defined subclasses of Filter* classes to perform encoding on input and output streams.
• Threads:
  • SimpleThread.java and SimpleThreadObj.java show two implementations of a simple program with two independent threads.
  • SharingThread.java shows use of a synchronized method to make sure at most one thread at a time executes.
  • ProducerConsumer.java shows use of synchronized methods, wait() and notifyAll() to coordinate among threads.
  • TestInterrupt.java shows use of interrupt(), suspend(), resume() to coordinate among threads.
  • SimplerThread.java is an even simpler threads example that demonstrates whether your system performs timeslicing (if you're curious).
• The Java AWT:
  • ShowString1.java creates a Frame object (window plus titlebar) and displays a string in it.
  • ShowString2.java is ShowString1.java modified to use my CloseableFrame class.
  • CloseableFrame.java defines a subclass of Frame that (unlike its superclass) responds to window-closing events.
  • SwitchedButton.java shows use of Button class, ActionListener interface.
  • CloseableFrameAlt.java is an alternate version of the CloseableFrame class.
  • SwitchedButtonAlt.java is an alternate version of SwitchedButton.java above, using setEnabled().
  • PowerOf2GUI.java shows providing a GUI for an object, using a named adapter class and getActionCommand(), setActionCommand() to process events.
  • PowerOf2GUIAlt.java is an alternate version of PowerOf2GUI.java, using anonymous inner classes as adapters.
  • ColorLabels.java shows setting different foreground and background colors for different components.
  • MirrorLine.java shows use of TextField class.
  • Layouts.java shows use of different layout managers.
  • MirrorArea.java shows use of TextArea class and a variety of listener adapters. Compare with MirrorLine previously.
  • ListExample.java shows use of List class. ListExampleAlt.java is an alternate implementation.
  • ChoiceExample.java shows use of Choice class.
  • MenuExample.java shows use of Menu class.
  • PopupMenuExample.java shows use of PopupMenu class.
  • CheckboxExample.java shows use of Checkbox and CheckboxGroup classes.
  • ScrollExample.java shows use of Scrollpane class.
  • DialogExample.java shows use of Dialog class.
  • ChooseFont.java shows use of Font class (allows you to see effects of different font choices on label text).
  • ShowThreads.java provides utility methods for showing information about what threads are executing -- in case you are curious about what threads the AWT
  • DrawingFrame.java is an extension of the Frame class that (1) responds to window-closing events and (2) provides methods to get / set the size of the frame's "drawing area" (area excluding borders).
  • TestPattern.java is an application version of the TestPattern example in the text, demonstrating the use of the Graphics class to draw geometric figures.
  • TestPatternDB.java is an alternative version of TestPattern above, using double buffering to reduce flicker.
  • PolyDraw.java illustrates use of Canvas and Graphics classes in a simple drawing example.
  • Scribble.java, a modified application version of the DoodlePad example in the text, illustrates use of Canvas and Graphics classes in another simple drawing example.
  • ShowImage.java illustrates use of the Image class to display an image from a GIF or JPEG file. See sample GIF files tu_seal.gif (Trinity U. seal) and smiley.gif (smiley face).
  • ShowImageApplet.java is an applet version of the preceding example, with its corresponding HTML file ShowImageApplet.html.
  • ShowImageWithObserver.java illustrates use of the Image class to display an image from a GIF or JPEG file, specified via a URL. This program includes a mostly gratuitous ImageObserver that reports on progress as the image is loaded.
  • ColorPan.java illustrates generating an Image from pixel data.
  • BlackWhiteStatic.java illustrates generating a succession of images from pixel data.
  • ColorSep.java illustrates the use of filters with images.
• Java and networking:
  • DateAtHost.java illustrates use of java.net.* classes to retrieve time/date from a remote host.
  • ShowURLContents.java illustrates use of java.net.* classes to retrieve and display URL contents.
  • TinyHttpd1.java illustrates use of java.net.* classes to set up a very simple Web server (see comments in code).
  • TinyHttpd2.java illustrates use of java.net.* classes to set up a slightly less simple Web server (see comments in code).
  • UDPserver.java and UDPclient.java illustrate use of java.net.* classes for simple client/server communication using UDP.
  • Request.java, RequestServer.java, and RequestClient.java illustrate use of java.net.* classes and object serialization for more complex client/server communication using TCP. ( TestRequest.java tests the Request class and its subclasses.)

Other possibly useful classes

• Input class (methods for reading primitives and strings from standard input): Input.java. See TestInput.java, TestFileInput.java, TestInputLoop.java for additional examples of usage.
• Assertions class (methods to check assertions at runtime): Assertions.java.
• Closeable Frame class (version of java.awt.Frame): CIS3020CloseableFrame.java.
• IsItArt example application (example of simple Java graphics): IsItArt.java. Requires Input, Assertions, and CIS3020CloseableFrame above, and also RandomInts.class. Note that the latter is a .class file; no source is available.
• LineInput class (readLine() method for standard input that should work for all systems): LineInput.java. Note that LineInput.readLine(), unlike the methods of the Input class above, signals end of file by returning a null reference rather than by throwing an exception.