public ArrayRealVector(ArrayRealVector v1,ArrayRealVector v2){
  data=new double[v1.data.length + v2.data.length];
  System.arraycopy(v1.data,0,data,0,v1.data.length);
  System.arraycopy(v2.data,0,data,v1.data.length,v2.data.length);
}

public ArrayRealVector ( ArrayRealVector v1 , ArrayRealVector v2 ) { data = new double [ v1 . data . length + v2 . data . length ] ; System . arraycopy ( v1 . data , 0 , data , 0 , v1 . data . length ) ; System . arraycopy ( v2 . data , 0 , data , v1 . data . length , v2 . data . length ) ; }
construct a vector by appending one vector to another vector .
