JevaGUI: Java Evaluator --- Expressions & Statements, Graphical User Interface

Applet: If you're viewing this page in a Java Plug-in 1.2.2 capable browser (such as, on Microsoft Windows, Communicator 3.00 or later, or IE 3.02 or later, or on Solaris, Communicator 4.05 or later), you should be able to try out Jeva and Jexa below. (It may take a few minutes to download the plug-in if necessary, and then load the ~350KB jar file over the network and start the applet.) If your browser does not yet support a Java 1.2 plug-in, you can point the Sun's JDK appletviewer at the URL of this page to run the applet button:   appletviewer http://www.ai.mit.edu/people/caroma/tools/1999-06-09/JevaGUIApplet.html
Appletviewer won't display this surrounding text. Alternatively, if your browser does support Java 1.1, you may still try out an earlier version.

Evaluating

• Try a simple expression like 3 + 4 and press "Evaluate".
• Try (use copy and paste):
  import java.util.*;
  new Date(System.currentTimeMillis())
Note that Jeva parses as much as it can to create an statement or expression, leaving the rest in the pane, so press "Evaluate" once for the import statement, and then once again for the new expression.
• Previous results are in:   localResults.get(n) 
  so you can name previous values with something like:
  Date myDate = (Date) localResults.get(2);
• Jeva is useful for exploring libraries. Try:
  import java.text.DateFormat;
  DateFormat.getDateInstance(DateFormat.SHORT, Locale.JAPAN).format(myDate)

• Print to the result pane with:   localOut.println("Hello.");  (If used in an application rather than from an applet's security box, JevaGUI can redirect System.out to the result pane as well.)
• For inspecting/debugging applets, an applet parameter can tell JevaGUI to bind   localApplet  to the applet, via which other applets on the page may be accessed.

Interoperating with Jexa

• Try:   myDate  and press "Evaluate", then press "Examine Result".
• Alternatively, try   Jexa.examine(myDate)  
  (Note that when JevaGUI started up, it silently did  import edu.mit.ai.psg.jexa.Jexa  for your convenience.)
• Try complex (or ridiculous) parses like   ~1*2+3^4%5|6&7>>>8  and press "Parse"; then press "Examine Result" to examine the resulting parse tree to see if you understand the precedence order.
• Try   Jexa.examine(localApplet)  
• Navigate from the applet, to its first panel, to the title label. Click on it to bring up the popup menu (Mouse-R, i.e., usually the right mouse button, or shift-click depending on your platform). Select "Set Jexa.mousedObject = (this)".
• Now we can change its colors to maroon and gray by evaluating the following:
  import java.awt.*;
  Label myTitle = (Label) Jexa.mousedObject;
  myTitle.setForeground(Color.lightGray);
  myTitle.getParent().setBackground(Color.decode("#800000"));