question: public ThumbnailParameterBuilder scale ( double widthScalingFactor , double heightScalingFactor ) { if ( widthScalingFactor <= 0.0 || heightScalingFactor <= 0.0 ) { throw new IllegalArgumentException ( "Scaling factor is less than or equal to 0." ) ; } else if ( Double . isNaN ( widthScalingFactor ) || Double . isInfinite ( widthScalingFactor ) ) { throw new IllegalArgumentException ( "Scaling factor must be a rational number." ) ; } else if ( Double . isNaN ( heightScalingFactor ) || Double . isInfinite ( heightScalingFactor ) ) { throw new IllegalArgumentException ( "Scaling factor must be a rational number." ) ; } this . widthScalingFactor = widthScalingFactor ; this . heightScalingFactor = heightScalingFactor ; return this ; }
target:  Sets the scaling factor of the thumbnail.