Vec2 (version 3) Methods, static and otherwise

// Vec2 version 3, static methods

public class Vec2 {
   private String name;
   private double kx, ky;

   public Vec2(String name, double kx, double ky) {
      this.name = name;
      this.kx = kx;
      this.ky = ky;
   }

   public Vec2(double kx, double ky) {
      this.kx = kx;
      this.ky = ky;
   }

   public void setName(String name) {
      this.name = name;
   }

   public String getName() {
      return name;
   }

   public void setVec(double kx, double ky) {
      this.kx = kx;
      this.ky = ky;
   }

  public double getX()  {
       return kx;
  }

  public double getY() {
      return ky;
  }

   public String toString() {
      String s = "(" + kx + " " + ky + ")";
      if (name==null) return s;
      return name + " = " +s;
   }

   static public Vec2 sum(Vec2 a, Vec2 b) {
      return new Vec2(a.kx+b.kx,a.ky+b.ky);
   }
	
   static public Vec2 diff(Vec2 a, Vec2 b) {
      return new Vec2(a.kx-b.kx,a.ky-b.ky);
   }

   // returns magnitude of 2D vector
   public double magn() {
      return Math.sqrt(kx*kx+ky*ky);
   }

   final static double radg = Math.atan(1.0)/45.0;

   // returns dot product
   static public double dot(Vec2 a, Vec2 b) {
      return (a.kx*b.kx+a.ky*b.ky);
   }

   // returns cross product
   static public double cross(Vec2 a, Vec2 b) {
      return (a.kx*b.ky-a.ky*b.kx);
   }


   // returns angle (in degrees) between two vectors
   static public double angle(Vec2 a, Vec2 b) {
      double c, s;
      c = dot(a,b);
      s = cross(a,b);
      return Math.atan2(s,c)/radg;
   }



   static public void main(String[] args) {
      Vec2 A = new Vec2("A",3.0,4.0);
      Vec2 B = new Vec2("B",2.0,-1.0);

      Vec2 sum = Vec2.sum(A,B);

      System.out.println(A+"\n"+B+"\nsum = A+B = "+sum);

      Vec2 diff = Vec2.diff(sum,B);
      System.out.println("sum - B = " + diff);

      System.out.println("magnitude(A) is "+A.magn());

      System.out.format("Angle from B to A:  %g%n" , Vec2.angle(B,A));
   }



}