JevaES: Java Evaluator --- Expressions & Statements

prerelease version of 1999.10.11
Copyright (c) 1997, 1998, 1999 Massachusetts Institute of Technology.
This software is provided "as is" without express or implied warranty.
Contains parser generated by Sun's JavaCC/JJTree from a modified version of the example Java grammar.

JevaESCLI is a command line interface (e.g., it can optionally be used within a Gnu Emacs M-! or M-x shell as shown at right). By default it reads from System.in, which cannot be used by multiple threads simultaneously (including debugger threads in jdb).

JevaESGUI is a graphical (windowed) user interface to JevaES. It creates a window for each invocation so it is possible to interact with multiple threads concurrently. It also highlights syntax errors. Editing is via mouse cut and paste. JevaESGUI can also be used as an applet; try the examples on its applet page.

The results of expressions can be examined using Jexa, the Java Examiner. In turn, objects found through navigation can be used to set the value of Jexa.mousedObject, so that they are accessible for use in method calls. (See applet page.)

Used as Applet: JevaESGUI can be used as an applet on a page. If there are other applets on the page, it can be used to interact with those applets. (See applet page.)

Called from programs: JevaESGUI can be used to experiment with your own programs. Its read-eval-print-loop (REPL) can be invoked from programs which provide values of variables to inspect or manipulate. A JevaESGUI REPL can return values (or throw exceptions) back to programs, so it can be used in a program stub which asks the user to type in code to compute the result.

See the jevaESUI package javadoc for more details.

Jeva (experimental)

1999-07-05: Jeva: Fixed infinite loop bug reading java files that crept into the 1999-06-09 release.

1999-06-09: Jeva: Jeva's eval hook has been extended to be called after a construct's subexpressions have been evaluated, just before the construct is 'applied', for recording call traces; this required making the parse tree less flat for operators. CompileUnit.setTempRoot(..) can now be used to enable compiled proxy classes to be reused between sessions. Added Jeva.runClass(..). Shortened names of option bits in Jeva and JevaGUI. Bound localOut and localErr to the local output pane PrintWriters; bound localResults to access the results in JevaCLI, JevaESCLI, JevaGUI, and JevaESGUI. Fixed bugs in interpreted constructors with parameters of interpreted type, explicit constructor calls, method synchronization. JevaES and Jeva: Fixed bugs in ...== null, casting, || and &&, accessibility of members of non-public classes; import by name now correctly overrides import on demand. Localization: JevaESUI and JevaUI may be localized; button and prompt strings are properties that may be overridden according to language of default locale for international use (however, JevaES error messages are not localizeable in this version).

1999-02-28 : Package statements can be used to change the current package for access to package protected fields and methods. Java1.2 reflection permits access to non-public fields and methods (may require ReflectPermission). Jeva adds interpreted classes, evalhook to JevaES.

1998-12-02: compatible with Java 1.1.

Related Systems:

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  • JavaCC/JJTree by Sun's test division (now maintained by the spin off Metamata along with a redesigned version, MParse) was among the first Java parsers in Java available, and is used in Jeva/JevaES. It has some features not available in others, such as the ability to preserve comments. It is free, but not yet open-source.
  • JTB, a Java Tree Builder that works with JavaCC in place of JJTree. It is less flexible about what tree gets built from the grammar, but may provide cleaner access to nodes.
  • ANTLR, an open-source parser generator with a less Java-like grammar syntax.
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