com.singularsys.jep
Class Variable

java.lang.Object
  java.util.Observable
      com.singularsys.jep.Variable

All Implemented Interfaces:

java.io.Serializable

public class Variable
extends java.util.Observable
implements java.io.Serializable

Information about a variable. Each variable has a name, and a value. There is a flag to indicate whether it is a constant or not (constants cannot have their value changed). There is also a flag to indicate whether the value of the variable is valid. If the variable is initialized without a value then its value is said to be invalid.

This class extends java.util.Observable allowing observers to track if the variable value has been changed. Use addObserver(Observer o) to add an observer. When the variable value is changed the Observer's update(o, arg) method is called, the first argument is the Variable object and the second is the object representing the new value.

Version:

2.3.0 beta 2 Now extends Observable so observers can track if the value has been changed.

Author:

Rich Morris Created on 18-Nov-2003

See Also:

Serialized Form

Field Summary

protected java.lang.String

name

Constructor Summary

protected	Variable(java.lang.String name) Constructors are protected.
protected	Variable(java.lang.String name, java.lang.Object value) Constructors are protected.
protected	Variable(Variable var) Copy constructor

Method Summary

java.lang.String	getName() Returns the variable name.
java.lang.Object	getValue() Returns the variable's value.
boolean	hasValidValue() Is the value of this variable valid?
boolean	isConstant() Returns true if the variable is a constant.
void	setIsConstant(boolean b) Setting this property to true ensures that the value will not be changed.
void	setValidValue(boolean val) Sets whether the value of variable is valid.
boolean	setValue(java.lang.Object object) Sets the value of the variable.
boolean	setValue(java.lang.Object object, java.util.Observer observer) Sets the value of the variable.
protected boolean	setValueRaw(java.lang.Object object) In general subclasses should override this method rather than setValue.
java.lang.String	toString() Returns a string with the variable name followed by it's value.

Methods inherited from class java.util.Observable

addObserver, clearChanged, countObservers, deleteObserver, deleteObservers, hasChanged, notifyObservers, notifyObservers, setChanged

Methods inherited from class java.lang.Object

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

Field Detail

name

protected java.lang.String name

Constructor Detail

Variable

protected Variable(java.lang.String name)

Constructors are protected. Variables should only be created through the associated VariableFactory which are in turned called by VariableTable.

Variable

protected Variable(java.lang.String name,
                   java.lang.Object value)

Constructors are protected. Variables should only be created through the associated VariableFactory which are in turned called by VariableTable.

Variable

protected Variable(Variable var)

Copy constructor

Parameters:

var -

Method Detail

getName

public java.lang.String getName()

Returns the variable name.

Returns:

the variable name.

isConstant

public boolean isConstant()

Returns true if the variable is a constant.

setIsConstant

public void setIsConstant(boolean b)

Setting this property to true ensures that the value will not be changed.

Parameters:

b - true if the variable is a constant.

getValue

public java.lang.Object getValue()

Returns the variable's value.

Returns:

the Variable value as Object.

hasValidValue

public boolean hasValidValue()

Is the value of this variable valid?

setValidValue

public void setValidValue(boolean val)

Sets whether the value of variable is valid. Constant values are not affected, that is always valid.

setValue

public boolean setValue(java.lang.Object object)

Sets the value of the variable. Constant values cannot be changed.

This method calls java.util.Observable.notifyObservers() to indicate to anyone interested that the value has been changed. Note subclasses should override setValueRaw rather than this method so they do not need to handle the Observable methods.

This method sets the validValue flag to true.

Returns:

false if tried to change a constant value.

Since:

2.3.0 beta 2 added Observable

setValue

public final boolean setValue(java.lang.Object object,
                              java.util.Observer observer)

Sets the value of the variable. The observer argument is passed to all observers update method. This can help an observer detect if set the variables value itself, and can lead to a performance boost.

Parameters:

object -

observer -

Returns:

false if tried to change a constant value

setValueRaw

protected boolean setValueRaw(java.lang.Object object)

In general subclasses should override this method rather than setValue. This is because setValue notifies any observers and then calls this method.

This method sets the validValue flag to true.

Parameters:

object -

Returns:

false if tried to change a constant value.

Since:

2.3.0 beta 2

toString

public java.lang.String toString()

Returns a string with the variable name followed by it's value. For example for the variable "a" with the value 10, the following string is returned:

a: 10

If the variable is a constant the string " (Constant)" is appended.

Overrides:

toString in class java.lang.Object

Returns:

A string with the variable name and value.