public class Particle {

  protected Vector3D position;
  protected Vector3D initialPosition;  
  protected Vector3D velocity;
  protected Vector3D force;
  protected float mass;
  protected float age;
  protected boolean dead;
  boolean fixed;
  protected int id;
  ArrayList<Particle> linkedNodes;
  
 // ArrayList springs;

  public Particle( float m )
  {
    position = new Vector3D();
    initialPosition = new Vector3D();
    velocity = new Vector3D();
    force = new Vector3D();
    mass = m;
    fixed = false;
    age = 0;
    dead = false;
    linkedNodes = new ArrayList();
    //ArrayList springs = new ArrayList();
  }



  /* (non-Javadoc)
   
   * @see traer.physics.AbstractParticle#distanceTo(traer.physics.Particle)
   
   */

  public final float distanceTo( Particle p )

  {

    return this.position().distanceTo( p.position() );
  }



  /* (non-Javadoc)
   
   * @see traer.physics.AbstractParticle#makeFixed()
   
   */

  public final void makeFixed()

  {

    fixed = true;

    velocity.clear();
  }



  /* (non-Javadoc)
   
   * @see traer.physics.AbstractParticle#isFixed()
   
   */

  public final boolean isFixed()

  {

    return fixed;
  }



  /* (non-Javadoc)
   
   * @see traer.physics.AbstractParticle#isFree()
   
   */

  public final boolean isFree()

  {

    return !fixed;
  }



  /* (non-Javadoc)
   
   * @see traer.physics.AbstractParticle#makeFree()
   
   */

  public final void makeFree()

  {

    fixed = false;
  }



  /* (non-Javadoc)
   
   * @see traer.physics.AbstractParticle#position()
   
   */

  public final Vector3D position()

  {

    return position;
  }

public final Vector3D initialPosition()

  {

    return initialPosition;
  }



  public final Vector3D velocity()

  {

    return velocity;
  }



  /* (non-Javadoc)
   
   * @see traer.physics.AbstractParticle#mass()
   
   */

  public final float mass()

  {

    return mass;
  }



  /* (non-Javadoc)
   
   * @see traer.physics.AbstractParticle#setMass(float)
   
   */

  public final void setMass( float m )

  {

    mass = m;
  }



  /* (non-Javadoc)
   
   * @see traer.physics.AbstractParticle#force()
   
   */

  public final Vector3D force()

  {

    return force;
  }



  /* (non-Javadoc)
   
   * @see traer.physics.AbstractParticle#age()
   
   */

  public final float age()

  {

    return age;
  }



  protected void reset()

  {

    age = 0;

    dead = false;

    position.clear();

    velocity.clear();

    force.clear();

    mass = 1f;
  }
}