public class Segment {
private iVector m_start, m_end;
public Segment(iVector start, iVector end) {
m_start = start;
m_end = end;
}
iVector getStart() {
return m_start;
}
iVector getEnd() {
return m_end;
}
double len() {
return (m_end.sub(m_start)).len();
}
double distanceTo(iVector point) {
 /* iVector a;
if (len() == 0) {
return m_start.sub(point).len();
}
a = m_end.sub(m_start).multiply(1 / len());
iVector b=point;
b.sub(m_start);
double s = a.scalar(b);
a = m_start.add(a.multiply(s));
s = a.sub(point).len();
if (m_start.sub(point).len() < m_end.sub(point).len()) {
if (m_start.sub(point).len() < s) {
s = m_start.sub(point).len();
}
} else {
if (m_end.sub(point).len() < s)
s = m_end.sub(point).len();
}
return s;*/
double s;
double P=((point.sub(m_start)).scalar(m_end.sub(m_start));//скалярное произведение двух векторов
double L=(m_end.sub(m_start)).scalar(m_end.sub(m_start));
if (0>=P) s=point.sub(m_start).len();//длина вектора
if (P>=L) s=point.sub(m_end).len();
if (0<P && P<L) s=point.sub(m_start.add((m_end.sub(m_start)).multiply(P/L))); }
public static void main(String args[]) {
 // Vector2D start=new Vector2D();
 // Vector2D end= new Vector2D(1,0);
 // Vector2D point=new Vector2D(0.5,0.5);
Vector start = new Vector(4);
Vector end = new Vector(new double[] { 1, 0, 0, 0 });
Vector point = new Vector(new double[] { -1, 0, 0, 0 });
Segment seg = new Segment(start, end);
System.out.println(seg.distanceTo(point));
}
}
}