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Class JavaAgent.resource.fopl.Symbol 

java.lang.Object
   |
   +----JavaAgent.resource.fopl.Symbol
public class Symbol
extends Object
This class implements the foundations for symbolic programming in Java. At the moment a Symbol is basically a String that is its name. Using the Symbol class should be slightly more efficient than using Strings and there may be extensions in future.

The cunning thing about Symbols is that there is only one Symbol with any given name. They are memory-unique objects. This saves memory if the same Symbol is used frequently and allows for efficient equality testing by comparing handles instead of content.

See Also:
UnnamedSymbol

Variable Index

o theName
the name of the Symbol

Constructor Index

o Symbol(String)
This protected constructor is used mainly by the static function get() to create new Symbols.

Method Index

o clone()
Cloning a Symbol returns the same Symbol, not a copy!
o equals(Object)
This function tests whether two Symbols are the same.
o get(String)
This function must be used to get hold of Symbols with the given name.
o hashCode()
The hashCode() of a Symbol is the hashCode() of the String that is its name.
o toString()
A Symbol is printed as the String that is its name.

Variables

o theName 
 protected String theName
the name of the Symbol

Constructors

o Symbol 
 protected Symbol(String aName) throws IllegalArgumentException
This protected constructor is used mainly by the static function get() to create new Symbols.

Parameters:
aName - the name of the new Symbol
Throws: IllegalArgumentException
An exception will occur if the supplied String is empty or null.

Methods

o get 
 public static Symbol get(String aName) throws IllegalArgumentException
This function must be used to get hold of Symbols with the given name. It effectively replaces a public constructor. For example,

Symbol mySy = Symbol.get("Foo");

initializes mySy with the Symbol named "Foo". If a Symbol with the given name has been gotten before, this very Symbol will be returned. Otherwise get() will use the protected constructor to create the new Symbol.

Parameters:
aName - the name of the Symbol seeked
Returns:
the Symbol with the given name
Throws: IllegalArgumentException
An exception will occur if the supplied String is empty or null.
o clone 
 public Object clone()
Cloning a Symbol returns the same Symbol, not a copy!

Returns:
this Symbol
Overrides:
clone in class Object
o equals 
 public boolean equals(Object otherSy)
This function tests whether two Symbols are the same. The test compares the physical address in memory and should thus be more efficient than String comparison. Note that there cannot be two different Symbols with the same name.

Parameters:
otherSy - the Object this one is compared to
Returns:
whether the other Object is the same as this
Overrides:
equals in class Object
o toString 
 public String toString()
A Symbol is printed as the String that is its name.

Returns:
the String that is the name of this Symbol
Overrides:
toString in class Object
o hashCode 
 public int hashCode()
The hashCode() of a Symbol is the hashCode() of the String that is its name.

Returns:
the hashCode of this Symbol's name
Overrides:
hashCode in class Object 
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