question: public boolean isCollinearWith ( Vector other ) { if ( x == 0 && y == 0 && z == 0 ) { return true ; } final double otherX = other . x ; final double otherY = other . y ; final double otherZ = other . z ; if ( otherX == 0 && otherY == 0 && otherZ == 0 ) { return true ; } if ( ( x == 0 ) != ( otherX == 0 ) ) return false ; if ( ( y == 0 ) != ( otherY == 0 ) ) return false ; if ( ( z == 0 ) != ( otherZ == 0 ) ) return false ; final double quotientX = otherX / x ; if ( ! Double . isNaN ( quotientX ) ) { return other . equals ( multiply ( quotientX ) ) ; } final double quotientY = otherY / y ; if ( ! Double . isNaN ( quotientY ) ) { return other . equals ( multiply ( quotientY ) ) ; } final double quotientZ = otherZ / z ; if ( ! Double . isNaN ( quotientZ ) ) { return other . equals ( multiply ( quotientZ ) ) ; } throw new RuntimeException ( "This should not happen" ) ; }
target:  Returns whether this vector is collinear with another vector.