2D Vector class

public class Vec {
    public final static Vec X_AXIS=new Vec(1,0);
    public final static Vec Y_AXIS=new Vec(0,1);
    public final static Vec ORIGIN=new Vec(0,0);

    final double x,y;

    public Vec(double x, double y) {
        this.x=x;
        this.y=y;
    }
    public double dotProduct(Vec v) {
        return x*v.x+y*v.y;
    }
    public double crossProduct(Vec v) {
        double r=x*v.y-y*v.x;
        return r;
    }
    public double angle() {
        return Math.atan2(y,x);
    }
    public double angleTo(Vec v) {
        double angle=v.angle()-angle();
        while(angle <= -Math.PI) angle+=Math.PI*2;
        while(angle > Math.PI) angle-=Math.PI*2;
        return angle;
    }
    public double getLength() {
        return Math.sqrt(x*x+y*y);
    }
    public Vec translate(Vec v) {
        return new Vec(this.x-v.x, this.y-v.y);
    }
    public Vec rotate90() {
        return new Vec(-y, x);
    }
    public Vec rotate270() {
        return new Vec(y, -x);
    }
    public Vec rotate180() {
        return new Vec(-x, -y);
    }
    public Vec rotate(double theta) {
        double sin = Math.sin(theta);
        double cos = Math.cos(theta);
        return new Vec(x*cos-y*sin,
                       x*sin+y*cos);
    }
    public Vec normalize() {
        double length=getLength();
        if(length==0) return X_AXIS;
        return new Vec(x/length, y/length);
    }
    public Vec add(Vec v) {
        return new Vec(x+v.x, y+v.y);
    }
    public Vec sub(Vec v) {
        return new Vec(x-v.x, y-v.y);
    }
    public Vec mul(double m) {
        return new Vec(x*m, y*m);
    }
    public Vec div(double d) {
        return new Vec(x/d, y/d);
    }
    public Vec neg() {
        return new Vec(-x, -y);
    }
    public String toString() {
        return String.format(java.util.Locale.ENGLISH,
        "(%.3f, %.3f)", x, y);
    }
}