Command line arguments get their name because they are included in the command to run a Java byte code using JDK as run from the DOS prompt. We will discuss how to do this after the midterm. BlueJ prompts you for the command line arguments everytime you run a main program.

To read from an input file, do the following:

1. Add the line import java.io.*;
   to the beginning of the source code.

2. Add throws IOException after the declaration of the main method.

3. Declare and create a FileReader object passing it the file name string.

4. Declare and create a BufferedReader object passing it the reference variable to the FileReader. A BufferedReader object is able to read one line at a time.

5. Everytime you want to read a line, use readLine method of BufferedReader. When you reach the end of the file, readLine will return a null string.

6. After the midterm, we will process files with more than one field per line. We will then use a StringTokenizer object to parse the information in the line.

Go over Day4 Examples StaffMember in Day4.zip or Day4.txt.
Here is the inheritance hierarchy for the StaffMember Example:

Go over Day4 Example Celest in Day4.zip or Day4.txt.
Here is the inheritance hierarchy for the Celest Example:

A class B inherits a class A when all the instance variables in A can also be used in class B. This is accomplished in Java by this class declaration:
public class A extends B

Here is a table showing some of the terms used to describe the class A and B, which have an inheritance relationship:

Class A	Class B
Base Class	Derived Class
Class	Subclass
Superclass	Class
Parent Class	Child Class

Use the line
super(arg1, arg2, arg3, ...);
to invoke the consructor in the parent class.

A method can be overridden in a derived class by supplying a method definition with name and signiture identical to those of the overridden in the base class. To invoke the overridden method of the base class, use super.methodname(arg1, arg2, arg3, ...);