The Rectangle Class

CONSTRUCTOR  

new Rectangle (< double >,  < double >) -- < rectangle >  

OPERATORS  

< rectangle > .length () -- < double >  

< rectangle > .width () -- < double >  

< rectangle > .area () -- < double >  

< rectangle > .perimeter () -- < double >  

< rectangle > .diagonal () -- < double >  

Commands  

< rectangle > .display ()  

PROBLEM:  

Suppose we have a city block of length 480 and width 300 partitioned into 16 rectangular lots.  

/ /Model the block and a lot in terms of rectangles.         double blockLength = 480;         double blockWidth = 300;         Rectangle block = new Rectangle (blockLength,         blockWidth);         double lotLength = blockLength / 8.0;         double lotWidth = blockWidth / 2.0;         Rectangle Lot = new Rectangle (lotLength,         lotWidth);     / /Display the distance from one corner of the block         to the far corner.         IO.println (block.diagonal ());     / /Declare a variable called pc and bind it to a percent         of the block taken up by one lot.         double pc = (lot.area () /block.area ()) * 100.0;

 

PROBLEM:  

What is the surface area of a cylinder of height 28.5 and diameter 11.6?  

Note > The surface area of the cylinder equals the area of the top + the area of the bottom + the area of the side.  

We will use problem decomposition to solve this problem.   We can ``explode'' the cylinder into two circles and a rectangle.  

?   class -- SurfaceAreaApp   ?   Needs -- import blue.shapes.   *;   ?   Program       / /Establish the given information.           double cylinderHeight = 28.5;           double cylinderDiameter = 11.6;       / /Create the top.           double topRadius = cylinderDiameter / 2.0;           Circle top = new Circle (topRadius);       / /Create the bottom.           double bottomRadius = topRadius;           Circle bottom = new Circle (bottomRadius);       / /Create the side.           double sideHeight = cylinderHeight;           double sideLength = top.perimeter ();           Rectangle side = new Rectangle (sideHeight,           sideLength);       / /Compute the surface area of the cylinder.           double sa = top.area () + bottom.area () +           side.area ();       / /Display the result.           IO.println (``The surface area =  ``+ sa +           ``square units.'')

 

String Manipulation  

< String > + < String > -- < String >  

Example:       ``sun'' + ``shine'' -- ``sunshine''

 

< String > + < int > -- < String >  

Example:       ``x =  ``+ 5.2     means ``x =  ``+ ``5.2''     means ``x = 5.2''