1. Programming for Beginners Martin Nelson Elizabeth FitzGerald Lecture 12: Programming Project

2. Revision of session 11 Java has in-built techniques for handling errors: Place ‘dangerous’ code inside a try statement. If this code generates an error, it throws an exception. Immediately after the try statement, we have a catch statement, which contains instructions for how to handle various types of exception. File I/O can be done using the class RandomAccessFile Mode can be “r” (read-only) or “rw” (read-write). All file I/O must be error-trapped, i.e. inside a try statement. Useful method for reading data: readLine Useful method for writing data: writeBytes

3. Session 12 – aims and objectives Programming project! Using all the concepts which we’ve covered in the course so far: Software design – pen & paper!! Pseudocode. Coding, bit by bit. Software testing. Successive refinement.

4. Programming Project Task: Create an address book program, capable of storing the contact details of a number of your friends. Make a class called “Person”, with variables to store name, address, phone number and email address. Your program should store a number of friends in an array. Ask the user to choose between adding new friends, updating old friends’ information, or search for a friend by name. Store the contact info in a text file.

5. Programming Project This task will take some time – there is a lot to do! Break the task down into smaller chunks... Create the Person class. Store some people in an array manually. Add User input. Add methods to manipulate data. Add File I/O. Remember: Pen & paper first! Pseudocode! Test the code after every step!

6. How do I exit? You may like to loop your code, repeatedly asking the user to add friends, update contacts, search for people etc. until they get bored... Can use a perpetual loop to do this... while(true){ do_stuff }; If you do this, make sure you give the user the choice to quit the program. To end the program neatly: System.exit(0); Don’t worry about this until everything else in your code works properly!

7. The File Class – 1 You may find that a convenient way to update your contacts file is to delete the old version, and re-populate the list from scratch. The File class contains a number of methods for manipulating files. For example, to delete the file contacts.txt: File myFile = new File(“contacts.txt”); myFile.delete(); The File class also contains methods for testing read/write access to a given file/directory, and much more. See the documentation for more details.

8. The File Class – 2 Do not confuse File with RandomAccessFile! File class: manipulating files and directories testing for existence testing read/write access creating/deleting files/directories extracting file properties. RandomAccessFile class: reading data from files writing data to files.

9. Coming up in Sessions 13-15 Some new languages, other than Java! Session 13: A brief introduction to C++ Session 14: A brief introduction to scripting languages. Session 15: Overview of some more-advanced concepts Some ideas that we should be aware of for efficient coding. Some more interesting java tasks, e.g. graphics! Where to go next? Future C++ and Java programming courses.