public ArrayRealVector(double[] v1,double[] v2){
  final int l1=v1.length;
  final int l2=v2.length;
  data=new double[l1 + l2];
  System.arraycopy(v1,0,data,0,l1);
  System.arraycopy(v2,0,data,l1,l2);
}

public ArrayRealVector ( double [ ] v1 , double [ ] v2 ) { final int l1 = v1 . length ; final int l2 = v2 . length ; data = new double [ l1 + l2 ] ; System . arraycopy ( v1 , 0 , data , 0 , l1 ) ; System . arraycopy ( v2 , 0 , data , l1 , l2 ) ; }
construct a vector by appending one vector to another vector .
