CMSC 202H — Fall 2011

Lab10 Class

We maintain an array students of Student objects to hold the student records. Also, we maintain the number of student records in the variable numStudents. The fileReader is the Scanner object used for reading from the file.

1. Perform number of arguments check: Check if the user has entered the right number of command line arguments needed by the program. We need the filename, so there must be one parameter passed. If no parameter is passed to the program, display an appropriate error message and exit.

   How will you know how many command line arguments were passed in?

2. Assign the file's input stream to the Scanner object fileReader: The file's input stream is available using a FileInputStream object, which is initialized using the filename. This FileInputStream object is in turn used to initialize the Scanner object. This code may throw a FileNotFoundException, so use the appropriate try and catch blocks. In this step, we are creating an object of the Scanner class and assigning it to the fileReader reference variable.

   How will you know the name of the file?

3. Read the number of student records from the file: The first line in the file contains the number of students. Store this value as numStudents.

   Which method of the Scanner object can you use to read in integer values from the file?

4. Allocate memory for the array: As we now know the number of student records, we can now create an array with the appropriate size to hold all of the student records.

5. Store the students' records: Read from the file line by line using the Scanner object. For every record in the file, create a new Student object, initialize its values with those given in the file, and store the Student object in the students array.

   How do you detect the end-of-file?

   How do you read the tuple from each line?

6. Close the file: Always remember to close the file's input stream when you are done reading the file.

   Which method will you use to close the input stream ?

7. Print stored records: Print the information stored in the student array in the form:

   Student name = [name] and id = [id]

   Since the catch block is only handling the FileNotFoundException, what will happen if we get some other kind of exception?