/***  CelestialBody class supports record keeping and computation concerning
properties of stars, planets, and moons.

Draft -bds 9/21/98 - built from basic version in Arnold/Gosling.
***/

import java.io.*;

public class CelestialBody {

// instance data
  private long idNum;
  private String name = "<unnamed>";
  private CelestialBody orbits = null;  
	   // the body around which this one orbits.
  private double radius = 0.0;
  private double density = 0.0;
  private double majorAxis = 0.0;
  private double minorAxis;

// class data

  private static long nextID = 0; // shared var to allow unique id's.
  private final static double PI = 3.145926535;
  private final static int majorVersion = 0;
  private final static int versionUpdate = 0;

// constructors
  CelestialBody() {
    idNum = nextID++;
  }

  CelestialBody(String bodyName, CelestialBody whatItOrbits) {
    this(); // get done what the no arg constructor does.
    name = bodyName;
    orbits = whatItOrbits;
  } // constructor

  CelestialBody(String bodyName, CelestialBody whatItOrbits, 
                double itsRadius, double itsDensity, 
                double itsMajorAxis, double itsMinorAxis) {
    this( bodyName, whatItOrbits);
    radius = itsRadius;
    density = itsDensity;
    majorAxis = itsMajorAxis;
    if ( itsMinorAxis < 0.0 )
      minorAxis = majorAxis;
    else
      minorAxis = itsMinorAxis;
  } // constructor

// methods

  public double volume() {
    return area()*radius/3.0;
  } // method volume

  public double area() {
    return 4.0*PI*radius*radius;
  } // method area

  public static void displayVersion () {
    System.out.println("Using CelestialBody class version " 
			+ Integer.toString(majorVersion)
			+ "."
			+ Integer.toString(versionUpdate)
                      );
  } // class method displayVersion

} // class CelestialBody

/* Examples of declaring and using CelestialBodies
(in a method (main, for instance) of another class

CelestialBody planets[10]; //sun at 0, pluto at 9.

CelestialBody sun = new CelestialBody( "Sol", null); 
CelestialBody earth = new CelestialBody( "Earth", sun); 

planet[0] = sun;
planet[4] = new CelestialBody( "Mars", planet[0], 1000.0, ... );

  x = earth.radius; // doesn't work, radius is private
  y = earth.volume();
  Sysrem.out.print( sun.area() );

  CelestialBody.displayVersion();

*/