public class Fourvector extends Threevector{

	private double tcoord;

	Fourvector()
	{
		super(); //not strictly required, it happens by default, included for clarity
		tcoord = 0.0;
	}
	Fourvector(double t, double x, double y, double z)
	{
		super(x,y,z);
		tcoord = t;
	}
	Fourvector(double t, Threevector v)
	{
		super(v);
		tcoord = t;
	}
};