com.singularsys.jepexamples.consoles
Class Console

java.lang.Object
  java.awt.Component
      java.awt.Container
          java.awt.Panel
              java.applet.Applet
                  com.singularsys.jepexamples.consoles.Console

All Implemented Interfaces:

java.awt.event.KeyListener, java.awt.image.ImageObserver, java.awt.MenuContainer, java.io.Serializable, java.util.EventListener, javax.accessibility.Accessible

Direct Known Subclasses:

BigDecimalConsole, CPConsole, PostfixEvaluationConsole, PrefixDumperConsole, PrintConsole, VectorConsole

public class Console
extends java.applet.Applet
implements java.awt.event.KeyListener

This class implements a simple command line utility for evaluating mathematical expressions.

   Usage: java com.singularsys.jepexamples.consoles.Console [expression]
 

If an argument is passed, it is interpreted as an expression and evaluated. Otherwise, a prompt is printed, and the user can enter expressions to be evaluated.

This class and its subclasses can also be run as a java applet which displays a textarea for interactive input.

This class has been designed to be sub classed to allow different consol applications. The methods

 public void initialise()
 public void processEquation(Node node) throws Exception
 public boolean testSpecialCommands(String command)
 public void printPrompt()
 public void printIntroText()
 public void printHelp()
 

can all be overwritten.

Furthermore main should be overwritten. For example

 
        public static void main(String args[]) {
                Console c = new DJepConsole();
                c.run(args);
        }

The main input loop is approximately

 initialise();
 printIntroText();
 print(getPrompt());
 String command;
 while((command = getCommand()) != null) 
 {
        if(command.equals("quit") || command.equals("exit"))
                break;
        if(!testSpecialCommands(command)) continue;
   try {
          Node n = j.parse(command);
          processEquation(n);
   } catch(Exception e) {}
        print(getPrompt());
 }

See Also:

Serialized Form

Nested Class Summary

static class

Console.SPEC_ACTION

Nested classes/interfaces inherited from class java.applet.Applet

java.applet.Applet.AccessibleApplet

Nested classes/interfaces inherited from class java.awt.Panel

java.awt.Panel.AccessibleAWTPanel

Nested classes/interfaces inherited from class java.awt.Container

java.awt.Container.AccessibleAWTContainer

Nested classes/interfaces inherited from class java.awt.Component

java.awt.Component.AccessibleAWTComponent, java.awt.Component.BaselineResizeBehavior, java.awt.Component.BltBufferStrategy, java.awt.Component.FlipBufferStrategy

Field Summary

protected Jep	jep Main Jep object
protected java.awt.TextArea	ta Text area for user input in applets.

Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Fields inherited from interface java.awt.image.ImageObserver

ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

Constructor Summary

Console()
Constructor

Method Summary

java.lang.String	getAppletInfo()
protected java.lang.String	getCommand() Get a command from the input.
java.lang.String	getPrompt() Prints the prompt string.
boolean	handleError(java.lang.Exception e) Handle an error in the parse and evaluate routines.
void	init() Applet initialization
void	initialise() sets up all the needed objects.
void	inputLoop() The main input loop for interactive operation.
void	keyPressed(java.awt.event.KeyEvent arg0)
void	keyReleased(java.awt.event.KeyEvent event) Handles keyRelease events
void	keyTyped(java.awt.event.KeyEvent arg0)
static void	main(java.lang.String[] args) Creates a new Console object and calls run()
void	print(java.lang.Object o) Prints a line of text no newline.
void	printFuns() Prints a list of defined functions.
void	printHelp() Print help message.
void	printIntroText() Prints introductory text.
void	println(java.lang.Object o) Prints a line of text no newline.
void	printOps() Prints a list of defined operators.
void	printStdHelp() Prints a standard help message.
void	printVars() Prints a list of variable.
boolean	processCommand(java.lang.String command) Process a single command.
void	processEquation(Node node) Performs the required operation on a node.
void	run(java.lang.String[] args) The main entry point with command line arguments
java.lang.String[]	split(java.lang.String s) Splits a string on spaces.
Console.SPEC_ACTION	testSpecialCommands(java.lang.String command) Checks for special commands.

Methods inherited from class java.applet.Applet

destroy, getAccessibleContext, getAppletContext, getAudioClip, getAudioClip, getCodeBase, getDocumentBase, getImage, getImage, getLocale, getParameter, getParameterInfo, isActive, newAudioClip, play, play, resize, resize, setStub, showStatus, start, stop

Methods inherited from class java.awt.Panel

addNotify

Methods inherited from class java.awt.Container

add, add, add, add, add, addContainerListener, addImpl, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getAlignmentX, getAlignmentY, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getComponentZOrder, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getInsets, getLayout, getListeners, getMaximumSize, getMinimumSize, getMousePosition, getPreferredSize, insets, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicyProvider, isFocusTraversalPolicySet, layout, list, list, locate, minimumSize, paint, paintComponents, paramString, preferredSize, print, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, removeNotify, setComponentZOrder, setFocusCycleRoot, setFocusTraversalKeys, setFocusTraversalPolicy, setFocusTraversalPolicyProvider, setFont, setLayout, transferFocusBackward, transferFocusDownCycle, update, validate, validateTree

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, createVolatileImage, createVolatileImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getBackground, getBaseline, getBaselineResizeBehavior, getBounds, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocation, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPeer, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isBackgroundSet, isCursorSet, isDisplayable, isDoubleBuffered, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPreferredSizeSet, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, reshape, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFocusable, setFocusTraversalKeysEnabled, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setMaximumSize, setMinimumSize, setName, setPreferredSize, setSize, setSize, setVisible, show, show, size, toString, transferFocus, transferFocusUpCycle

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

jep

protected Jep jep

Main Jep object

ta

protected java.awt.TextArea ta

Text area for user input in applets.

Constructor Detail

Console

public Console()

Constructor

Method Detail

init

public void init()

Applet initialization

Overrides:

init in class java.applet.Applet

initialise

public void initialise()

sets up all the needed objects.

main

public static void main(java.lang.String[] args)

Creates a new Console object and calls run()

run

public void run(java.lang.String[] args)

The main entry point with command line arguments

inputLoop

public void inputLoop()

The main input loop for interactive operation. Repeatedly calls getCommand() and processCommand().

processCommand

public boolean processCommand(java.lang.String command)

Process a single command.

1. Tests for exit, quit, and help.
2. Tests for any special commands used by sub classes. testSpecialCommands(String)
3. Parses the command.
4. Processes the node. processEquation(Node)
6. Checks for errors. handleError(Exception)

Parameters:

command - The line to be processed

Returns:

false if un-recoverable error or 'quit' or 'exit'

processEquation

public void processEquation(Node node)
                     throws JepException

Performs the required operation on a node. Typically evaluates the node and prints the value.

Parameters:

node - Node representing expression

Throws:

JepException - if a Parse or evaluation error

getCommand

protected java.lang.String getCommand()

Get a command from the input.

Returns:

null if an IO error or EOF occurs.

getPrompt

public java.lang.String getPrompt()

Prints the prompt string.

printStdHelp

public final void printStdHelp()

Prints a standard help message. Type 'quit' or 'exit' to quit, 'help' for help.

printHelp

public void printHelp()

Print help message.

printIntroText

public void printIntroText()

Prints introductory text.

printFuns

public void printFuns()

Prints a list of defined functions.

printOps

public void printOps()

Prints a list of defined operators.

printVars

public void printVars()

Prints a list of variable.

testSpecialCommands

public Console.SPEC_ACTION testSpecialCommands(java.lang.String command)

Checks for special commands. For example a subclass may have a verbose mode switched on of off using the command

verbose on

This method can be used detected this input, perform required actions and skip normal processing by returning true. In general sub classes should call the superclass methods to test for special commands that class implements

Parameters:

command -

Returns:

SPEC_ACTION.CONTINUE - continue processing this equation, SPEC_ACTION.BREAK - stop processing this equation and get the next line of input, SPEC_ACTION.EXIT stop the program

See Also:

split(String)

handleError

public boolean handleError(java.lang.Exception e)

Handle an error in the parse and evaluate routines. Default is to print the error message for JepExceptions and a stack trace for other exceptions

Parameters:

e -

Returns:

false if the error cannot be recovered and the program should exit

split

public java.lang.String[] split(java.lang.String s)

Splits a string on spaces.

Parameters:

s - the input string

Returns:

an array of the tokens in the string

print

public void print(java.lang.Object o)

Prints a line of text no newline. Subclasses should call this method rather than System.out.print to allow for output to different places.

println

public void println(java.lang.Object o)

Prints a line of text no newline. Subclasses should call this method rather than System.out.print to allow for output to different places.

keyReleased

public void keyReleased(java.awt.event.KeyEvent event)

Handles keyRelease events

Specified by:

keyReleased in interface java.awt.event.KeyListener

keyPressed

public void keyPressed(java.awt.event.KeyEvent arg0)

Specified by:

keyPressed in interface java.awt.event.KeyListener

keyTyped

public void keyTyped(java.awt.event.KeyEvent arg0)

Specified by:

keyTyped in interface java.awt.event.KeyListener

getAppletInfo

public java.lang.String getAppletInfo()

Overrides:

getAppletInfo in class java.applet.Applet