com.singularsys.jep

Class Variable

java.lang.Object

java.util.Observable

com.singularsys.jep.Variable

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

BoundVariable, XVariable

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:

Richard Morris Created on 18-Nov-2003

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected Node.HookKey[]	keys
protected java.lang.Object[]	keyVals
protected java.lang.String	name

Constructor Summary

Constructors

Modifier	Constructor and Description
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

Modifier and Type	Method and Description
java.lang.Object	getHook(Node.HookKey key) Get the value associated with a key.
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?
java.util.Collection<Node.HookKey>	hookKeys() Return all the hooks set for this variable.
boolean	isConstant() Returns true if the variable is a constant.
java.lang.Object	removeHook(Node.HookKey key) Remove a hook from a variable
java.lang.Object	setHook(Node.HookKey key, java.lang.Object value) Sets the value associated with a key.
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

keys

protected Node.HookKey[] keys

keyVals

protected java.lang.Object[] keyVals

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?

Returns:

whether the value is 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 it 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 calls this method and then notifies any observers.

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

getHook

public java.lang.Object getHook(Node.HookKey key)

Get the value associated with a key.

Parameters:

key - the key to look up

Returns:

the value or null if no key exists

Since:

3.5

setHook

public java.lang.Object setHook(Node.HookKey key,
                                java.lang.Object value)

Sets the value associated with a key.

Parameters:

key - the key

value - the value

Returns:

the old object associated with this key, may be null

Since:

3.5

hookKeys

public java.util.Collection<Node.HookKey> hookKeys()

Return all the hooks set for this variable.

Returns:

a list of all the hooks

Since:

3.5

removeHook

public java.lang.Object removeHook(Node.HookKey key)

Remove a hook from a variable

Parameters:

key -

Returns:

the value of the removed hook or null if hook not found

Since:

3.5

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.