This homework will help you learn how to solve problem with multiple Java classes.

The objectives of this week are following:

• Programming abstraction of simple enrollment system.
• Learn more about class composition relationship.
• Using constructor to initialized class data type.
• Using "this" and "super" keywords.

##Post Class

• Base class for user post

##MessagePost Class

• One of Post's subclasses.
• Represent a message post which contains a single message for each post.

##PhotoPost Class

• One of Post's subclasses.
• Represent a photo post which contains filename of a photo and a caption for the photo.
• the photo file must be .jpg or .png.

##NewsFeed Class

• Represent a single news feed.
• Each news feed contains multiple posts.
• Each post can be message or photo.

##TestPost1 Class

• A test program which gives a result as those stored in the "TestPost1-output.txt" file

To complete the homework you need to meet following requirements:

• Output from the "TestPost1.java" program should be the same as or very similar to the output stored in the "TestPost1-output.txt".
• Draw a class and object diagram showing the relationship among the classes and objects.