Assignment 1: Calculation

Assigned: Wednesday, January 26, 1999
Due: Wednesday, February 3, 1999

In this assignment, you will create and test a class, SequenceComputer, that will perform a number of sequence-based computations.

This is an optional assignment. It will provide a small amount of extra credit if completed on time. It will also provide a valuable exercise to help you learn Java.

The SequenceComputer Class

Create a class, SequenceComputer, that does computations based on sequences of numbers presented to it. What computations do we typically do based on sequences? We might compute the sum of the numbers in the sequence or the average of the numbers in the sequence. Your class must support the following methods.

• double average() --- compute the average of the numbers in the sequence.
• double sum() --- compute the sum of the numbers in the sequence.
• int length() --- compute the length of the sequence.

You may be asking yourself how we present the sequence of numbers to SequenceComputer. We will do so through an addNumber method, defined as follows:

• void addNumber(double num) --- add a number to the sequence of numbers.

Your class must also support this method.

Finally, your SequenceComputer class should support a reset method, that resets the class to the empty sequence.

Notes

You may be asking yourself ``How do I represent a sequence?'' It turns out that the particular computations above do not require you to remember the whole sequence, simply some facts about the sequence. You will use fields to remember those facts. (And yes, it is a challenge to you to decide what facts to remember.)

You may also be asking yourself ``What should I do if someone asks me for the average in an empty sequence?'' We'll say that it's illegal to do so, and you can do whatever you want in such cases. In class 7 we'll discuss some possibilities.

Testing Your Class

Once you've built your SequenceComputer class, how should you test it? One possibility is to create a class that does some basic tests. For example,

import SimpleOutput;
import SequenceComputer;

/**
 * Test the cool SequenceComputer class.
 * 
 * @author Your Name Here
 * @version 1.0 of January 1999
 */
public class SCTester {
  /**
   * Test away!
   */
  public static void main(String[] args) {
    // Prepare for output.
    SimpleOutput out = new SimpleOutput();
    // Prepare for computation.
    SequenceComputer fred = new SequenceComputer();
    // Tell fred about the sequence.
    fred.addNumber(3.5);
    fred.addNumber(1);
    fred.addNumber(6);
    // Print some information.
    out.print("The average of 3.5, 1, and 6 is: ");
    out.println(fred.average());
    out.print("The sum of 3.5, 1, and 6 is: ");
    out.println(fred.sum());
    // Start a new sequence.
    fred.reset();
    out.print("After resetting, the sequence has length ");
    out.println(fred.length());
    // And so on and so forth.
  } // main(String[])
} // class SCTester

Extend the SCTester class to do additional testing and record the output.

Extra Credit

Do none, some, or all.

• Extend SequenceComputer to compute the minimum and maximum values in the sequence. (Easy)
• Extend SequenceComputer to compute the second smallest value in the sequence. (Harder)
• Build a class that asks the user what to do (e.g., add an element to the sequence, reset the sequence, print the average, etc.) and, using SequenceComputer, does what the user has asked. (Not too hard, but requires loops, which we won't cover until class 6.)
• Build a class that reads a 0-terminated sequence of numbers and, using SequenceComputer, computes the average and sum of that sequence. (Not too hard, but requires loops, which we won't cover until class 6.)