question: public ArrayFieldVector ( Field < T > field , T [ ] v1 , T [ ] v2 ) throws MathIllegalArgumentException , NullArgumentException { MathUtils . checkNotNull ( v1 ) ; MathUtils . checkNotNull ( v2 ) ; if ( v1 . length + v2 . length == 0 ) { throw new MathIllegalArgumentException ( LocalizedCoreFormats . VECTOR_MUST_HAVE_AT_LEAST_ONE_ELEMENT ) ; } data = MathArrays . buildArray ( field , v1 . length + v2 . length ) ; System . arraycopy ( v1 , 0 , data , 0 , v1 . length ) ; System . arraycopy ( v2 , 0 , data , v1 . length , v2 . length ) ; this . field = field ; }
target:  Construct a vector by appending one vector to another vector.