JPT 2.7.0 Applets Page

Back to JPT 2.7.0

Updated on April 3, 2008

This site will be updated as additional applets are available.

List of Applets

To execute any applet, click on its screen snapshot. On each applet page, there is a link to the source files.

MethodsApplet Sample

String Method Tester

Kaleidoscope

Link to 2.6.0 Applets

MethodsApplet Sample

The MethodsApplet sample illustrates the use of the base class JPFApplet to enable Java Power Framework in an applet. This facilty is the most important addition to JPT 2.7.0.

The Methods Applet Sample permits the user to select from 4 buttons.

• The button TestGraphics will draw two filled shapes, a rectangle and an oval. Since these are added as Paintable objects, they may be clicked or dragged with the mouse.
• The button TestGrid draws a grid on the BufferedImage that is used the paint the background of the graphics window. This grid appears to be underneath the two filled shapes as the shapes are dragged in the window.
• The button EvaluateDouble brings up an auxiliary GUI in which a double precision expression entered on the right may be evaluated and displayed on the left. The views are arranged in the same order as a method signature in Java.
• The button ReverseString brings up an auxiliary GUI in which a string may be entered in the top panel and then “reversed” by clicking the evaluation button.

Here is a snapshot of the EvaluateDouble auxiliary GUI:

Here is a snapshot of the ReverseString auxiliary GUI:

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String Method Tester

Added January 25, 2008, 2:30 PM

The initial posting of this applet on January 24, 2008 failed due to the fact that JPT used getDeclaredMethods in class Class. It turns out that even asking for all declared methods causes a Java security exception in an applet deployed in a browser. Why this should be so is something of a puzzle since you have not yet called any methods. It is also the case that the same code works locally in AppletViewer so as a test program AppletViewer cannot be trusted.

The classes JPFHelper and JPFPane have been modified to work around this security issue. Now the method getMethods in class Class is used instead.

Discussion

This applet illustrates the fact that the core JPF class JPFPane may be called by other applications and applets to serve interesting purposes. This expands the value of the JPF reflection technology beyond the classes JPF and JPFApplet

The applet will test most methods in the Java String class against a string that may be specified by the user. The original applet pane has two areas: an area to enter a multi-line string to be tested and an area to specify the names of which String methods to test. If no names are given in this second area, then all possible String methods will be offered.

Once you enter a String to test in the top area and enter any method names, you may create a tester by clicking the button Create String Tester. The button extracts the test string from the top area and then creates a tester for that string. Since a String is immutable, if you change the test string you must create a new tester.

Here is a screen snapshot of the auxiliary GUI created to test any suitable method in the String class. You can see that you are given a scrolling list of method names and that if you hover over a button then the full signature of the method will be shown in a tool tip.

This auxiliary GUI is created by using JPFPane directly with the test string as its initializer and the method names to test (if any) as a filter.

Here is the additional auxiliary GUI created to test the method int indexOf(String).

You may confirm by counting that the index of lazy in the original test string is indeed 36.

More generally, this example shows that JPFPane may be used to test Java methods in a manner similar to what JPF and JPFApplet do for user-defined methods.

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Kaleidoscope

The KaleidoscopeApplet is a simulation of a kaleidoscope using Paintable objects created from shapes, images, and text. Historically, the concept of Paintable was defined in order to make this example possible. In earlier versions of JPT, this code was available only as an application. We decided to make this into an applet using our DirectApplet base class.

Here is a quick summary of the user options. These are also visible in the snapshot below.

• The items displayed in the kaleidoscope may be shapes or images or both. Up to 16 items may be displayed with a default of 12.
• Optionally, a large string “Kaleidoscope” may be displayed.
• The background may be white or black.
• The wedge angle that determines the angle of the kaleidoscope mirrors is set via an integer fraction N of 180 degrees.
• The wedge start angle simply sets where the mirrors will start. This angle changes by 1 degree in each animation step.
• The wedge is always visible during the animation. The user may choose whether or not to see the wedge when the animation is stopped.
• When the animation is stopped, the user may edit the picture by dragging an item. A clicked item moves to the top of the z-order.
• Because the code uses synchronization, the user may change the picture or other settings while the animation is running.
• Finally, the animation does not use physics. In a real kaleidoscope, the pieces inside tumble as the kaleidoscope is turned. I do not attempt to simulate this tumbling as the wedge turns about the center of the window. Instead, I permit the user to select various random transforms to distort the picture. This enables changes that could not occur in real life.

Click on the image to get to a button that will launch Kaleidoscope. Kaleidoscope is launched in its own window since it uses a large amount of screen real estate.

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