CS 1713 -- Spring 2001, Week 15

CS 1713-001 Introduction to Computer Science
Spring 2001 -- Lectures for Week 15

Week's Objectives:

Finish up Project 3. I just finished it myself, and here are some comments, including problems I had completing the assignment:
- I didn't have any problems finishing the first part, with files Balloon.java and BalloonMain.java, but at least one student was having trouble with the compareTo method in Balloon.java. This student was looking at other example compareTo methods, like the one from the text, say (page 296):
```
   public int compareTo (Object other)
   {
      int result;

      if (lastName.equals(((Contact)other).lastName))
         result = firstName.compareTo(((Contact)other).firstName);
      else
         result = lastName.compareTo(((Contact)other).lastName);

      return result;
   }
  
```
  This method is comparing Strings, using equals and compareTo for Strings. However, in the program Balloon.java, we are comparing doubles, and there is no equals for doubles. That is, you can't write something like d1.equals(d2) when d1 and d2 are doubles, but instead you must write d1 == d2.
- The other two files: WeatherBalloons.java and WeatherBalloonsMain.java were harder for me to finish, and I made a few mistakes.
  - I forgot to create an actual array of MAX many references to Comparable (which the method insert should use).
  - In printing balloons, I forgot that myBalloons[i] is a Comparable object and not a Balloon object, so it needs a cast (Balloon) in front of it.
  - The insert method is tricky, but I got it done quickly by just cribbing from the inside of the for loop in the insertion sort.
  - Doubling the size of the array is tricky. In case it is needed, you should create a new array twice as big as the old, then copy the old references to the new array, and then copy the reference to the whole new array in to overwrite the reference to the old array. In testing that the doubleArray method works, you should change MAX from 15 to 4 so that 2 doubling steps will be needed.
- Here is the output of my program WeatherBalloonsMain.java (your output doesn't have to look exactly the same):
```
Balloon 0: IdNumber: 111, ReleaseDay: 1, DistanceTraveled: 111.3
Balloon 1: IdNumber: 123, ReleaseDay: 2, DistanceTraveled: 143.7
Balloon 2: IdNumber: 972, ReleaseDay: 5, DistanceTraveled: 320.1
Balloon 3: IdNumber: 120, ReleaseDay: 1, DistanceTraveled: 370.2
Balloon 4: IdNumber: 531, ReleaseDay: 2, DistanceTraveled: 429.2
Balloon 5: IdNumber: 833, ReleaseDay: 4, DistanceTraveled: 433.1
Balloon 6: IdNumber: 143, ReleaseDay: 4, DistanceTraveled: 714.3
Balloon 7: IdNumber: 729, ReleaseDay: 2, DistanceTraveled: 726.1
Balloon 8: IdNumber: 629, ReleaseDay: 3, DistanceTraveled: 787.0
Balloon 9: IdNumber: 410, ReleaseDay: 5, DistanceTraveled: 820.4
Balloon 10: IdNumber: 621, ReleaseDay: 3, DistanceTraveled: 962.4
Balloon 11: IdNumber: 269, ReleaseDay: 3, DistanceTraveled: 976.4
Balloon 12: IdNumber: 460, ReleaseDay: 5, DistanceTraveled: 980.8
Balloon 13: IdNumber: 511, ReleaseDay: 1, DistanceTraveled: 1240.0
Balloon 14: IdNumber: 986, ReleaseDay: 4, DistanceTraveled: 1320.6
Day: 1, Max: 1240.0
Day: 2, Max: 726.1
Day: 3, Max: 976.4
Day: 4, Max: 1320.6
Day: 5, Max: 980.8
Day: 6, Max: 0.0
Balloon with id = 120 is
   IdNumber: 120, ReleaseDay: 1, DistanceTraveled: 370.2
Balloon with id = 100 not found
  
```

Revision date: 2001-04-26. (Please use ISO 8601, the International Standard.)

CS 1713-001 Introduction to Computer Science Spring 2001 -- Lectures for Week 15

CS 1713-001 Introduction to Computer Science
Spring 2001 -- Lectures for Week 15