Homework 4: Graphics, Applets and File I/O

• Review the example graphics files mentioned in Lecture 8.
• Create a directory named javahw4/ in your directory.
• Copy data files shapes1.txt and shapes2.txt into your javahw4/ directory.
• Create an HTML document named shapes.html and save into your javahw4/ directory.
  • The title of the document should be "Draw Shapes Applet by Your Name."
  • There should be two applet tags.
  • Each applet tag should use DrawShapesApplet.class as the code.
  • Each applet should have dimensions width 300 and height 200.
  • Each applet tag should contain one parameter "filename", the name of a text file.
    • Its value should be either "shapes1.txt" or "shapes2.txt".
• Create a class file named DrawShapesApplet.java and save into your javahw4/ directory.
  • Create the class definition: class DrawShapesApplet extends Applet
  • All other code should go into the paint() method of the class.
  • Use the applet's getParameter() function to get the name of the file from the param tag.
    • String filename = getParameter("filename");
  • The applet should open the specified file as follows:
URL fileURL = null;
URLConnection connection = null;
InputStream in = null;
try { fileURL = new URL(getDocumentBase(), filename); }
catch (MalformedURLException e) { System.out.print(e); }
try { connection = fileURL.openConnection(); in = connection.getInputStream(); }
catch (IOException e) { System.out.print(e); }
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
  • Use the readLine() function to read each line in the file.
    • Use a while loop to loop while the line is not null.
    • Wrap the entire loop in a try block and add an empty catch block (as above).
  • Create a StringTokenizer object to read each part of the line.
    • StringTokenizer st = new StringTokenizer(line);
    • String command = st.nextToken();
  • If the command is "color", use the next three numbers to change foreground color.
    • You will have to get three more tokens and cast to int.
  • Else if the command is "line", "rectangle", "oval" or "arc", display the filled shape with the coordinates listed.
    • You will have to cast each of the tokens to ints to get the coordinates.
  • Otherwise ignore the entire line.
  • Valid commands are as follows (all dimensions in integers):
    • color r g b
    • line x1 y1 x2 y2
    • rectangle x y width height
    • oval x y width height
    • arc x y width length startAngle arcAngle
  • The program should work for the two test data files and any other correct input file.
    • No other error or exception handling is required.
• Import the necessary classes:
  • Applet from java.applet
  • Graphics and Color from java.awt
  • InputStream, InputStreamReader, BufferedInputStream, BufferedReader and IOException from java.io
  • StringTokenizer from java.util
  • URL, URLConnection and MalformedURLException from java.net
• Compile the applet by typing javac DrawShapesApplet.java.
• Open shapes.html to test and debug the applet.
• Use Ark to create an archive of your directory named javahw4.zip.
• Send the source code to the instructor as an attachment in a message with subject java hw 4.