Lab 7: Shapes Revisited
- Read text data from a file using
- Employ exception handling to gracefully manage corrupt data files
- Throw an exception when invalid data is passed to a constructor
In this assignment you will revist the work you did for Lab 4.
In particular, you will write your own code to create a
instance and draw shapes in the window. The characteristics of the window
and the shapes to be drawn must be read from a file.
Shape Class Upgrades
First, you must revisit each of the classes implemented for lab 4:
You should incorporate any feedback you received from your instructor and
add checks to the constructors to ensure that no shape is created with
unrealistic dimensions. In particular, if a non-positive value is passed
to a constructor for one of the dimensions (width, height, base, radius), an
IllegalArgumentException with an appropriate message must be thrown.
You must also implement the
Point class described in lab 4.
You must implement a
ShapeLoaderApp class to replace the
you developed in Lab 4. Your implementation must read a file that contains
information about the picture, create a window, and then draw all of the
specified shapes on the window. The program must ask the user to select
a file; however, you may determine how you obtain the file location from
the user. An example file is shown below:
The file has the following format:
- Line 1: contains the title for the window
- Line 2: contains the dimensions of the window specified as integer values for width (first) and height (second) separated by whitespace
- Line 3: contains the background color for the image specified as a hex triplet (six-digit hexadecimal) color
- Line 4-end: contains the specification of a particular type of shape (one per line)
The shape formats are specified as:
- Point -
P: X Y COLOR
- Circle -
C: X Y COLOR RADIUS
- Triangle -
T: X Y COLOR BASE HEIGHT
- Rectangle -
R: X Y COLOR WIDTH HEIGHT
- Labeled Triangle -
LT: X Y COLOR BASE HEIGHT LABEL
- Labeled Rectangle -
LR: X Y COLOR WIDTH HEIGHT LABEL
- Although a single space is shown between each field of the shape specification, your program must allow for any non-newline whitespace to be present between fields. For example,
P: X Y COLOR(tab between
Y) should be considered as valid.
LABELcan contain non-newline whitespace. I.e., anything on the line after the
HEIGHTis considered to be part of the
ShapeLoaderApp must extend
Application and instantiate a
WinPlotterFX1 object, which extends
must implement the following methods:
start()— This method must make use of a
FileChooserto obtain the filename from the user. It must read the header information from the file (the first three lines) and create a
WinPlotterFXobject with the appropriate characteristics.
readShapes()— Reads all lines after the header information (lines 4 - end) and stores each shape in a
Listof shapes. This method uses the
parseShape()method to create the appropriate shape. If
parseShape()throws an exception, no shape is added for that line of the input file.
drawShapes()— Draws all of the shapes in the shape list.
main()— The main method just calls
parseShape()— Accepts a
Stringthat should contain one line from the input file and returns an instance of the appropriate shape. The line from the input file should represent one of the known shapes in the correct format. If the format does not match one of the specified shapes, an exception must be thrown (to be handled by the
stringToColor()— Accepts a
Stringthat should contain a hex triplet and returns a
Colorinstance of the appropriate color. If the argument is not a hex triplet (does not begin with the number symbol, is not seven characters long, or if any of the last six characters are not a valid hexadecimal digit), an
InputMismatchExceptionmust be thrown.
There are a number of situations that could cause your program to throw an exception. For example, if the file is not found, can't be opened, or contains incorrectly formatted data. If the program is unable to correctly read the picture header information (the first three lines) from the file, the program should display an appropriate
Alert dialog. The program should then end. If an error is encountered while reading a line of the file after the header information, a useful error message should be written to the console and the program should continue on to the next line in the file.
You should experiment with a number of input files containing invalid formatting. Without doing this it is unlikely that your code will handle all of the possible ways that things could go wrong.
1Just for Fun
You may choose to make use of the
WinPlotterFX class to do your drawing
or implement your own GUI to draw the shapes.
This laboratory assignment was developed by Dr. Chris Taylor.