Lecture 21

May 2, 2000

Exam 2 Post-Mortem

• Average grade was 69.3– Median was 72, which means there were some

very low scores that pulled down the average.

• There were 5 A’s, 6 B’s, 8 C’s, 5 D’s, and 8 F’s

• Answers to code questions on the web.

• Answers to short answers on your sheet.

FMQs

• Q 6: Remember, a subclass object is also a superclass object, but not vice-versa.– Update! I made a mistake on the answer key; the

correct choice was E. (No wonder so many people missed it.)

• Q 23: You can define an anonymous class anywhere, even inside a parameter list in a method call.

• Q 25: An event object always gets passed to a callback method in Java.– A listener is an object has a callback method.

Review: TextEdit.java

• Read the file from disk into the TextArea.

• User edits the TextArea in memory (RAM).

• Write the file from the TextArea to the disk.

Project: MP3 Tag Editor

• Overview– Read an MP3 file from disk into memory.– User edits the tags in memory.– Write the MP3 file from memory to disk.

• GUI Design Goals– Use appropriate Components.– Use layout managers so the user can change the

size of the main window.

MusicMatch Jukebox

• Download free copy:– http://www.musicmatch.com

• Can play MP3 music files.• Can generate MP3 music files from audio CDs.• Maintains a “library” of your MP3 music files.

– Provides an editor for your library.

• There are other MP3 programs available, such as winamp, realaudio jukebox, etc.

MP3 File Structure

ID3V2 Tag (optional)

Audio Information

ID3V1 Tag (optional)