noope.laws
Class Law

java.lang.Object
  |
  +--noope.laws.Law

Direct Known Subclasses:

OutputProjection, OutputText, ParticlePairLaw

public abstract class Law

extends java.lang.Object

This class describes a force-law in the modelled universe. Below is a skeleten example of how Law could be subclassed to create a useful law, for a full implementation see the Gravity class.

class GravityPropertyRecord extends LawPropertyRecord
{
GravityPropertyRecord(BlockReader, Entity) // get gravitation mass from BlockReader
protected double gravitationalMass;
public double getGravitationalMass();
}

class Gravity extends Law
{
Gravity(BlockReader br, int number, Physics phys)
{
super(br, number);
// do rest of initialization from br
}

LawPropertyRecord constructNewPropertyRecord(BlockReader r, Entity e)
{ 
return new GravityPropertyRecord(r, e);
}

public void act()
{ // for each entity in Entities
// work out force on it and call entity.addForce, by using entity.getPropertyRecord(lawnum)
}
...
}

Version:

19-Apr-2001 Added dispose() [Miklos Reiter]

Author:

Miklos Reiter

Field Summary

protected Physics

physics A reference to the physics world so getActiveForce can learn about its environment.

Constructor Summary

Law(BlockReader br, int lawnumber, Physics phys)
Constructs a new Law object from the supplied BlockReader, with lawnumber as its number.

Method Summary

abstract void	act() Make the law act upon the entities.
LawPropertyRecord	constructNewPropertyRecord(BlockReader br, Entity ent) Create a new LawPropertyRecord from the BlockReader object.
void	dispose() Dispose of system resources used by this law.
java.lang.String	getName() Returns the name of the law object.
int	getNumber() Returns the number of the law object.
java.lang.String	toString() Provides for debug-quality printing.

Methods inherited from class java.lang.Object

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

Field Detail

physics

protected Physics physics

A reference to the physics world so getActiveForce can learn about its environment.

Constructor Detail

Law

public Law(BlockReader br,
           int lawnumber,
           Physics phys)
    throws BRLoadingException

Constructs a new Law object from the supplied BlockReader, with lawnumber as its number. These numbers are allocated by the Laws constructor. Everything apart from the number is loaded from br. The constructor of every derived law should follow this interface. Subclasses should call the inherited constructor first to make sure the name is assigned. Also, subclasses, should have a constructor taking a BlockReader and an int, so it can be called by Physics, even though it does not know about the class. The entries in br have to be as follows:

[name "lawName"]
(if name not given as first entry, will assume classname, i.e. parameter as the name of the law)
... (custom entries for derived laws)
...

Parameters:

br - BlockReader used to initialise object

lawnumber - Number of this law

phys - Reference to the Physics world

See Also:

Laws.Laws(BlockReader, Physics)

Method Detail

getName

public java.lang.String getName()

Returns the name of the law object. This is as specified in the BlockReader object from which this Law object has been constructed.

getNumber

public int getNumber()

Returns the number of the law object. The number is the index of this Law in Laws and also the index of the corresponding LawPropertyRecord in Entity.properties

act

public abstract void act()

Make the law act upon the entities. This is called by Physics once in every time interval. This method should calculate the net force due to this Law acting on each Entity and then call Entity.addForce(force) on every Entity to add this law's constribution to the total force acting on the Entity.

Parameters:

e - the list of entities that the force should act on

See Also:

Entity.addForce(Vector3D)

constructNewPropertyRecord

public LawPropertyRecord constructNewPropertyRecord(BlockReader br,
                                                    Entity ent)
                                             throws BRLoadingException

Create a new LawPropertyRecord from the BlockReader object. This is done by calling the corresponding LawPropertyRecord's constructor with the BlockReader object. Most subclasses will want to override this method to construct an instance of their own LawPropertyRecord class, but this is not a requirement. If a law does not need to store any data, it can use the default method that just returns an instance of LawPropertyRecord. If this is what you want, pass it a null BlockReader object, or it will issue a warning.

Parameters:

br - BlockReader used to read properties from

ent - is the instance of Entity, this LawPropertyRecord will be constructed for

toString

public java.lang.String toString()

Provides for debug-quality printing. Print the name and number of this Law.

Overrides:

toString in class java.lang.Object

dispose

public void dispose()

Dispose of system resources used by this law. This can also be used for output laws to close any output devices like files, windows, etc. used. Added by Miklos Reiter on 19-Apr-2001.