question: public ArrayFieldVector ( FieldVector < T > v1 , T [ ] v2 ) throws NullArgumentException { MathUtils . checkNotNull ( v1 ) ; MathUtils . checkNotNull ( v2 ) ; field = v1 . getField ( ) ; final T [ ] v1Data = ( v1 instanceof ArrayFieldVector ) ? ( ( ArrayFieldVector < T > ) v1 ) . data : v1 . toArray ( ) ; data = MathArrays . buildArray ( field , v1Data . length + v2 . length ) ; System . arraycopy ( v1Data , 0 , data , 0 , v1Data . length ) ; System . arraycopy ( v2 , 0 , data , v1Data . length , v2 . length ) ; }
target:  Construct a vector by appending one vector to another vector.