Conversation started 2004-7-1 12:31:21

Information (12:31:21): chidhkratzer has joined the conference.
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Information (12:31:32): am out the door
nickbenn (12:31:34): Afternoon, all!
pamrdoodle2002 (12:31:48): hey there
Information (12:32:01): rsvr2956 has joined the conference.
chtkjohn (12:32:03): good afternoon.
rsvr2956 (12:32:08): HI
nickbenn (12:32:11): Did everyone get my e-mail from an hour ago?
shirleybirdteach (12:32:15): hello all I just updated our abstract file for Team One at
shirleybirdteach (12:32:22): will look
chtkjohn (12:32:37): i got it and am logged into mode
shirleybirdteach (12:32:49): I am also in mode
pamrdoodle2002 (12:32:49): i'm in mode also
nickbenn (12:32:56): Very good!
nickbenn (12:34:01): Ok. Let me tell what we're going to do: we're going to talk about our old friends, the kangaroos, again. This time, we're going to do some work with our Kangaroo "theme park" in Java.
nickbenn (12:34:14): All of our Java work will be done in Mode.
nickbenn (12:34:25): Any questions before we start?
nickbenn (12:35:09): Is anyone NOT logged on to the mode machine right now?
rsvr2956 (12:35:23): getting there
nickbenn (12:36:13): David, from what directory can the students copy the file?
nickbenn (12:37:19): Are you there, David?
Information (12:37:32): betty_strong2004 has joined the conference.
challengebetsy (12:37:46): Nick, if they go to the materials are at the bottom of the page.
chidhkratzer (12:37:47): cp /usr/local/scc/java/ .
nickbenn (12:37:54): perfect, thanks
nickbenn (12:38:03): Ok, folks, that's the command:
nickbenn (12:38:18): cp /usr/local/scc/java/ .
nickbenn (12:38:27): (there's a space before that last period)
nickbenn (12:38:53): Please type that, to copy a Java file we will be looking at, into your own directory on Mode.
Information (12:38:58): challengedianne has joined the conference.
chtkjohn (12:39:11): so do we need to change directories first?
chidhkratzer (12:39:33): You can stay in your home directory or.
nickbenn (12:39:35): the directory you are in by default, when you log on to mode, is fine.
nickbenn (12:40:24): Is anyone having problems copying the file?
shirleybirdteach (12:40:38): I am
chtkjohn (12:40:45): it accepted the command so I presume it worked
shirleybirdteach (12:40:47): command not found
pamrdoodle2002 (12:40:55): in my directory file it
nickbenn (12:41:05): make sure you have a space after the cp, shirley
nickbenn (12:41:10): Exactly, pam
betty_strong2004 (12:41:34): we typed in ours, but no error message or nothing happened
nickbenn (12:41:40): In Unix, no news is good news. But just to be sure, after you do the copy, you can type ls
shirleybirdteach (12:41:47): got it
nickbenn (12:41:47): and that will show you the directory contents.
nickbenn (12:42:03): Everyone have it?
betty_strong2004 (12:42:08): ok, its there
challengedianne (12:42:11): Should I be in mode to get the file?
nickbenn (12:42:35): you need to be logged in to Mode via Telnet, Dianne. We're going to work on Mode for this session.
nickbenn (12:43:24): Ok. Anyone still having problems with copying the file?
challengedianne (12:43:30): okay. If I am no longer participating it is because my computer locked up. I tried to get on mode yesterday with David and my computer froze.
rsvr2956 (12:43:48): ok, so after the is there...right
nickbenn (12:43:56): ok, Dianne
nickbenn (12:44:06): yep, should appear in your directory.
rsvr2956 (12:44:30): ok........I have to keep remembering the 'no news is good news'
nickbenn (12:44:47): Dianne, when you get logged in, please type the following (not the space after "cp", and another before the last period):
nickbenn (12:44:48): cp /usr/local/scc/java/ .
nickbenn (12:45:21): err, that should say (Note the space after "cp")
challengedianne (12:45:40): okay here I go
nickbenn (12:45:51): All right. Let's look at that file. Anyone have any idea how we should do that?
shirleybirdteach (12:46:11): pico
nickbenn (12:46:17): Exactly!
nickbenn (12:46:22): pico
nickbenn (12:46:29): Please note the uppercase K!!
nickbenn (12:46:37): and the space after the word "pico"
nickbenn (12:46:51): Everyone, please type the following:
rsvr2956 (12:46:54): I feel soooo PROUD...I got there
nickbenn (12:46:55): pico
nickbenn (12:47:19): Does everyone see some Java code on the Mode screen now?
betty_strong2004 (12:47:33): yes
nickbenn (12:47:41): Anyone not see it?
Information (12:47:50): chtvanob has joined the conference.
nickbenn (12:48:47): Ok...what do you first notice in this file, that looks like something we left out of the Excel version, on our first day?
nickbenn (12:49:30): How about four or five lines down?
pamrdoodle2002 (12:49:31): birthrate
nickbenn (12:49:56): And anything specific you notice about the birthrate, Pam?
pamrdoodle2002 (12:51:08): hummm I just don't know...really i can't read
nickbenn (12:51:19): Fair enough
pamrdoodle2002 (12:51:25): i don't know what is I do in excel
nickbenn (12:51:34): What we have, in those first few lines, is #1: Gender...
rsvr2956 (12:51:36): is it the ratio of fertility to mortality?
shirleybirdteach (12:51:42): fertility is not the same
nickbenn (12:51:51): #2, instead of a single birthrate, it looks like we have several different fertility rates.
chtkjohn (12:52:04): i missed a few things, got kicked off but it dind't tell me, how do open it?
nickbenn (12:52:09): #3, instead of a single death rate, it looks like we have several different mortality rates.
betty_strong2004 (12:52:12): here we can set the ratio of female to male?
pamrdoodle2002 (12:52:34): so the 3rd and 4th lines have changing rates?
nickbenn (12:52:44): Exactly right, Pam.
nickbenn (12:53:03): Now, go down a few lines more, and you will see "private int _age = 0;"
nickbenn (12:53:13): What is happening there?
pamrdoodle2002 (12:53:30): they all start out at age 0
nickbenn (12:53:35): Exactly
nickbenn (12:53:52): When a Kangaroo is born, it has an age of 0.
nickbenn (12:54:09): What are we doing in the next line down?
betty_strong2004 (12:54:29): determining the ratio of male to female
shirleybirdteach (12:54:36): randomly
rsvr2956 (12:54:49): Male to Female ratio
nickbenn (12:55:05): Yes, we're assigning gender randomly. On the average, what do you think that line is assuming about male-to-female ratio?
shirleybirdteach (12:55:17): 50% ratio
nickbenn (12:55:56): Very good. What we're doing is generating a random number between 0 and 1, and if that number is less that 0.5, we're assuming the kangaroo is male; otherwise, it's female.
nickbenn (12:56:00): Everyone clear on that?
chtkjohn (12:56:20): i think so
pamrdoodle2002 (12:56:50): yes...just don't understand the java...the grter than and less than symbols
nickbenn (12:57:09): ok. Now, let's think back to some of the things I said about Java classes: they are a sort of template, for creating t he "things" (objects) in our Java programs.
pamrdoodle2002 (12:57:22): and why we know that the number is between 0 and 1?
pamrdoodle2002 (12:57:49): how do we know that 1 is the other number Nick?
nickbenn (12:57:56): And when we define those classes, we define the data in them, as well as the actions that things made from the class know how to do.
nickbenn (12:58:34): Good question: we learn that by reading the Java documentation Math.random() is a method which returns a random number between 0 (inclusive) and 1 (exclusive).
pamrdoodle2002 (12:58:51): thanks
nickbenn (12:58:53): There are links to online java documentation, in the Java course page on WebCT, as well as on the Challenge site.
pamrdoodle2002 (12:59:06): thanks
chtkjohn (12:59:20): ? why is .25 repeated twice in the mortality and .3?
nickbenn (13:00:21): Well, I simply made these numbers up, but basically what they indicate are the birth and death rates in each year of life. So, the birth rate in the first year of a kangaroo's life is assumed to be 0, while the death rate is assumed to be 0.45 (45%).
challengedianne (13:00:34): I'm still having problems. Have to shut down. Will return ASAP Sorry!
Information (13:00:38): challengedianne has left the conference.
chtkjohn (13:00:44): gotch, thanks
nickbenn (13:00:51): In the second year of life, the birth rate is assumed to be 0.25, while the death rate is assumed to be 0.4.
nickbenn (13:01:02): ok, moving down:
nickbenn (13:01:33): Look at the line (you'll probably have to scroll) a bit in the mode screen that reads: "public void age () {"
nickbenn (13:02:26): Does everyone see that?
pamrdoodle2002 (13:02:31): yes
pamrdoodle2002 (13:02:47): does it clear the screen so you can start over?
nickbenn (13:03:10): This is the first line of what we call a "method". Methods are the actions that the different kinds of objects know how to do.
nickbenn (13:03:28): Go one lline down, and you will see "this._age++;"
nickbenn (13:03:54): The ++ operator in java is basically the same as saying:
nickbenn (13:04:02): this._age = this._age + 1;
nickbenn (13:04:12): in other words, we are incrementing the age.
nickbenn (13:04:32): So, what happens when we "tell" a kangaroo object to "age"?
shirleybirdteach (13:04:49): it gets one year older
nickbenn (13:05:06): Precisely.
rsvr2956 (13:05:51): mine stops after public void age <>
nickbenn (13:06:05): Press the arrow key down.
shirleybirdteach (13:06:06): you have to use the cursor
chidhkratzer (13:06:17): No mousing around on mode!
rsvr2956 (13:06:28): OH DAVID..........I needed that
nickbenn (13:07:01): If you look lower, you will also see a method called "breed", and one called "survive". Each of these uses a random number, and the FERTILITY and MORTALITY rates we saw above, to answer the questions: "Did this kangaroo breed successfully this year?" and "Did this kangaroo survive the year?"
nickbenn (13:07:32): Does everyone see those?
chtkjohn (13:07:42): i got booted again. yes
rsvr2956 (13:07:46): yes
pamrdoodle2002 (13:07:49): no
pamrdoodle2002 (13:07:53): yes
nickbenn (13:08:09): Now, you can see, in various places, the word "return". What do we think that means?
chtkjohn (13:08:09): Pam, do control V to see it
chtkjohn (13:09:06): whether or not to cycle through the program again?
pamrdoodle2002 (13:09:30): if you get a certain bit of is giving what to do then
nickbenn (13:10:05): Actually, return is much simpler than that. By itself, it simply means "stop executing the current method"; when it has something else to the right of it, it means "stop executing the current method, and pass this value or thing back to the code that called the method".
nickbenn (13:10:20): In the latter case, we can think of "return" as giving the answer to something we asked for.
nickbenn (13:11:09): So, look at the method "survive", and you will see that under a certain condition, we return true (the kangaroo did survive); otherwise, we return false (the kangaroo didn't survive).
nickbenn (13:12:00): Everyone with me?
rsvr2956 (13:12:14): yes
chtkjohn (13:12:14): sort of
betty_strong2004 (13:12:23): yes
nickbenn (13:12:25): "sort of" is fine
pamrdoodle2002 (13:12:30): thinking
nickbenn (13:12:56): Ok. look at the method "breed". It starts with the line "public Kangaroo breed () {
nickbenn (13:13:02): does everyone see it?
pamrdoodle2002 (13:13:19): y
chtkjohn (13:13:30): yes
nickbenn (13:13:39): Ok. Let me explain what this method does, in English:
nickbenn (13:13:47): The next line down says:
nickbenn (13:14:44): If the age of the kangaroo is less than the maximum age for which we have fertility data, and a random number (bewteen 0 and 1) that we generate is less than the fertility rate....
nickbenn (13:15:03): what do we think should happen then?
shirleybirdteach (13:15:23): you either have a birth or not
nickbenn (13:16:07): In this case, if we meet both of those conditions, we assume the kangaroo did breed - and in fact, the method returns a brand new Kangaroo object (see the next line down).
pamrdoodle2002 (13:16:09): well...when you are generating the number between 0 and 1....if it is a boy then you won't have a birth
pamrdoodle2002 (13:16:19): oh
nickbenn (13:16:23): Awesome, Pam! You just spotted the error we are going to fix now.
rsvr2956 (13:16:33):
nickbenn (13:16:41): Do we look at the gender of the kangaroo anywhere in these few lines??
shirleybirdteach (13:17:23): nope
pamrdoodle2002 (13:17:26): doesn't look like it to me
nickbenn (13:17:28): We'd better: if we tell a male to breed, he may do all sorts of things, but he can't give us a new Kangaroo. Only a female can do that
chtkjohn (13:17:40): got booted,
nickbenn (13:17:51): Make sense?
pamrdoodle2002 (13:17:55): y
chtkjohn (13:18:15): but where are aksing if its femal or not
nickbenn (13:18:23): Ok, so we need to add to our conditions. Basically we need to say:
shirleybirdteach (13:18:32): if it's not male then it must be female
Information (13:18:36): challengedianne has joined the conference.
challengedianne (13:18:46): Thanks Betsy
nickbenn (13:19:12): IF the kangaroo is female, and IF the kangaroo is not past bearing age, and IF the random number is within the right values, ONLY THEN do we get a new Kangaroo out of the deal.
nickbenn (13:19:13): Make sense?
pamrdoodle2002 (13:19:29): lot of conditions..but yes
chtkjohn (13:19:33): yes
nickbenn (13:20:15): So, put your cursor (using the arrow keys, not the mouse) on the line that starts with "if ((this._age < FERTILITY.length) && ..."
nickbenn (13:20:20): is everyone there?
chtkjohn (13:20:53): yes but popped up IM for some reason
chtkjohn (13:21:31): ready
nickbenn (13:21:45): Now, move your mouse to the second left parenthesis, and type the following:
nickbenn (13:21:55): ( ) &&
nickbenn (13:22:02): So that the line reads:
nickbenn (13:22:30): if (( ) && (this._age < FERTILITY.length) && ...
chtkjohn (13:22:50): done
nickbenn (13:23:08): By the way, any guesses on what "&&" means?
chtkjohn (13:23:26): and also, then also?
rsvr2956 (13:23:38): (()&& or () &&??
nickbenn (13:23:57): You add the ( ) && that the line reads:
nickbenn (13:24:06): if (( ) && (this._age < FERTILITY.length) && ...
nickbenn (13:24:19): (There will be two left parentheses right in a row)
rsvr2956 (13:24:25): ok
nickbenn (13:24:36): Any guesses on what "&&" means?
chtkjohn (13:25:17): yes it means "if then also" or "if and then also"
nickbenn (13:25:35): More simply, it means "AND ALSO"
nickbenn (13:26:03): Here, we are saying IF a AND ALSO b AND ALSO c, THEN do something.
nickbenn (13:26:24): ok, inside that first set of parentheses, we need to put a condition about gender.
chtvanob (13:26:33): is the line suppose to be: if (() && (this._age chtkjohn (13:26:40): Good old conditional statements!
nickbenn (13:26:52): Yes, exactly
nickbenn (13:27:30): Now, inside that first set of open parentheses, we need to put the condition about the gender of the Kangaroo
nickbenn (13:27:54): So, put your cursor (using the arrow keys) inside the empty parentheses, and type the following:
nickbenn (13:28:18): this.gender == MALE
nickbenn (13:28:26): (pay attention to case, again)
nickbenn (13:28:42): ack...sorry
nickbenn (13:28:46): That should say
chtkjohn (13:28:50): got booted, what are w3e putting for gender?
Information (13:28:50): irene_anne_lee has joined the conference.
nickbenn (13:28:55): this.gender == FEMALE
nickbenn (13:29:13): After you do that, the line should read:
nickbenn (13:29:25): if ((this.gender == FEMALE) && (this._age < FERTILITY.length) && (Math.random () < FERTILITY [this._age])) {
nickbenn (13:30:09): Does everyone have something that looks like that?
pamrdoodle2002 (13:30:34): y
chtkjohn (13:30:44): i think
chtvanob (13:30:52): got it
nickbenn (13:31:54): So now, in English, we would say this condition as "IF the gender of this kangaroo is female, AND ALSO the age of this kangaroo is within the maximum bearing age, AND ALSO the random number we generate is below the fertility rate threshold, THEN...
nickbenn (13:32:22): this kangaroo gives us a new baby kangaroo!
nickbenn (13:32:28): Otherwise... what happens?
shirleybirdteach (13:32:57): no new baby
nickbenn (13:33:15): Exactly. And, in fact, if we look below the line that reads "else {"
nickbenn (13:33:20): we see "return null"
nickbenn (13:33:43): which is the Java way of saying "we got nothing"
nickbenn (13:34:10): ANy questions?
chidhkratzer (13:34:28): We should writeOut the file now, right?
nickbenn (13:34:32): Ok, let's try to compile this program. On Mode, it's a bit more complicated than it was when we were using NetBeans, on monday.
nickbenn (13:34:36): First, write the file out.
nickbenn (13:35:06): type Ctrl-O
nickbenn (13:35:32): It will ask for a file name, but it should already say ""; if so, just hit enter.
nickbenn (13:36:21): Next, exit out of pico, by typing Ctrl-X
nickbenn (13:36:42): that will take you back to the mode prompt.
nickbenn (13:36:56): Is anyone not back at the Mode prompt yet?
nickbenn (13:37:57): Everyone with me?
chtkjohn (13:38:04): y
nickbenn (13:38:05): Ok
pamrdoodle2002 (13:38:09): y
betty_strong2004 (13:38:12): y
nickbenn (13:38:21): Now, we need to compile the java class file we just modified..
nickbenn (13:38:27): type:
nickbenn (13:38:33): javac
chtvanob (13:39:04): I have an error
nickbenn (13:39:06): (yes, there is a "c" at the end of "java", and there must be a space between that 'c" and "")
rsvr2956 (13:39:08): me too
nickbenn (13:39:29): What errors do you see?
shirleybirdteach (13:39:40): missing a ) after fertility.length
pamrdoodle2002 (13:39:42): clas or interface
chtvanob (13:39:51): ')' expected (Math.random () < FERTILITY [this._age])) { ^ 1 error
chtkjohn (13:40:45): sorry got booted, anything after javac
rsvr2956 (13:40:50): mine says Java:25: canot resolve symbol
nickbenn (13:40:56): now we're debugging
nickbenn (13:41:17): Most of the above look like some parentheses got mismatched when you edited the line.
chtkjohn (13:41:36): no news is good news right?
nickbenn (13:41:40): So, let's go back in pico, and make sure we got it right (it is very important to count parentheses).
nickbenn (13:41:45): Yes, no news is good news.
chtvanob (13:41:50): This is my line
chtvanob (13:41:55): if ((this.gender == FEMALE) && ((this._age chtvanob (13:42:11): Is that correct?
nickbenn (13:42:30): Now, to go back in pico, you can simply hit the up arrow from the mode prompt, a couple of times, and you will see the command "pico". When you do, hit enter
nickbenn (13:43:16): Vernetta, you've got an extra left parenthesis before "this._age < FERTILITY.length"
nickbenn (13:43:31): the line should read:
nickbenn (13:43:39): if ((this.gender == FEMALE) && (this._age < FERTILITY.length) && (Math.random () < FERTILITY [this._age])) {
rsvr2956 (13:43:55): are there spaces before/after the ==??
chtvanob (13:44:42): No new is good news - I GOT IT!
shirleybirdteach (13:45:01): if you put it anywhere but first it messes up your ()
chidhkratzer (13:45:06): Spaces are optional around the ==
nickbenn (13:45:08): Notice that there are two left parentheses before "this.gender", one right parenthesis after "FEMALE", one left parenthesis before "this._age", one right parenthesis after "FERTILITY.length", one left parenthesis before "Math.random()", and two right parentheses after "FERTILITY [this._age]"
shirleybirdteach (13:45:22): I put it last so it messed them up
shirleybirdteach (13:45:30): got it now
nickbenn (13:45:55): Re spaces before and after "==", they are not essential. However, having two equal signs, with no space between them, IS essential.
rsvr2956 (13:46:24): arrrrrgh....I still have an error
nickbenn (13:46:25): Ok, when you think you have fixed that line, write the file out again (Ctrl-O), and exit to the mode prompt (Ctrl-X)
nickbenn (13:46:57): Then compile again (you can use the up arrow trick again, or type "javac").
nickbenn (13:47:03): What error did you get this time?
chtkjohn (13:47:17): None again
rsvr2956 (13:47:25): the cannot resolve symbol symbol : variable Female
chidhkratzer (13:47:34): spell it FEMALE
nickbenn (13:47:39): did you type it as FEMALE, or Female?
nickbenn (13:47:44): Case is critical in Java!
rsvr2956 (13:47:48): OOOOOkay
nickbenn (13:48:41): There are also some recommended guidelines for naming and capitalization; links to these recommendations are on the Java course page of WebCT, as well as on t he Challenge site, in the Technical Guide page.
nickbenn (13:49:06): Ok, who doesn't yet have a clean compile?
rsvr2956 (13:49:22): great!!! i GOT IT...
pamrdoodle2002 (13:49:25): I can't get it to work...compile that is
nickbenn (13:49:34): What error are you getting, Pam?
pamrdoodle2002 (13:50:42): 2, class or interface expected...then 2 (Math.random () < FERTILITY...etc
chidhkratzer (13:50:46): Pam, take off the extra ( in front of this._age so that it is if ((this.gender == FEMALE) && (this._age < FERTILITY.length)
nickbenn (13:51:29): Yes, pam: please review the line EXACTLY as it appears above (when I typed it), and make sure your parentheses match mine.
nickbenn (13:51:53): Ok, for those who have successfully compiled,
nickbenn (13:52:22): there is another Java file we're going to copy. THis one, we aren't going to review at this time; we're just going to copy & compile it.
nickbenn (13:52:30): So, from the mode prompt, type:
nickbenn (13:52:57): cp /usr/local/scc/java/ .
nickbenn (13:53:07): (space after "cp", and space before the last period)
nickbenn (13:53:42): Is anyone not able to copy that?
challengebetsy (13:53:46): pamrdoodle2002
pamrdoodle2002 (13:54:08): not able
chtvanob (13:54:11): got it
nickbenn (13:54:26): did you get your Kangaroo class to compile, pam?
pamrdoodle2002 (13:54:30): no
pamrdoodle2002 (13:54:38): moving
rsvr2956 (13:54:48): ls now?
nickbenn (13:55:05): sure...for those that have compiled the first file, and copied the second, do an ls
nickbenn (13:55:18): you should see, Kangaroo.class, and
chtkjohn (13:55:32): y
rsvr2956 (13:55:41): yes
betty_strong2004 (13:55:43): y
nickbenn (13:55:43): Pam, if you have a few minutes after we wrap up here, I'll help you get back on track.
nickbenn (13:55:52): Ok, we're just going to compile the Zoo class.
nickbenn (13:55:53): type
nickbenn (13:56:00): javac
chtvanob (13:56:20): No news is good news!
nickbenn (13:56:23): everyone get that?
nickbenn (13:56:28): Indeed it is
shirleybirdteach (13:56:32): yes
chtkjohn (13:56:38): y
pamrdoodle2002 (13:56:43): okay...i can't do it because of the errors I got before right?
nickbenn (13:56:47): (You'll get an error on this next step, pam.)
pamrdoodle2002 (13:56:53): sure did
nickbenn (13:57:15): Ok. Zoo is not just a java class - it is also a Java program. Does anyone remember what makes a Java class a Java program?
shirleybirdteach (13:57:38): needs a main method
nickbenn (13:57:46): Exactly!
nickbenn (13:58:03): A java program will always have a method called "main", with a certain structure.
nickbenn (13:58:12): As it turns out, Zoo has this
Information (13:58:23): jkraloff2001 has joined the conference.
nickbenn (13:58:24): Since it does, we can "run" it.
nickbenn (13:58:30): And this is how we do so:
nickbenn (13:58:33): type:
nickbenn (13:58:40): java Zoo 100 10
rsvr2956 (13:59:32): poor kangaroos
nickbenn (13:59:40): Indeed!
nickbenn (13:59:49): Is everyone seeing a year-by-year tally?
shirleybirdteach (13:59:54): yes
chtkjohn (13:59:57): yes
chtvanob (13:59:57): yes
betty_strong2004 (13:59:58): yes
nickbenn (14:00:17): Let me quickly explain the command-line parameters Zoo is using:
nickbenn (14:00:44): the first is the # of Kangaroos to start with, and the second is the number of years to run (actually, Zoo has a bug, and runs a year longer than it should; that's my fault).
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nickbenn (14:01:00): So, try
nickbenn (14:01:08): java Zoo 500 20
chtkjohn (14:01:40): i think thke theme park is doomed
nickbenn (14:01:45): You'll still probably see numbers dwindling rapidly.
rsvr2956 (14:01:48): They die fast
shirleybirdteach (14:01:53): unless you enter some new blood
nickbenn (14:01:58): Yes.
nickbenn (14:02:22): Now, I'll cheat and tell you one problem with our program:
nickbenn (14:03:07): When the Zoo sets up the Kangaroo population with the specified number of Kangaroos, it uses that Kangaroo class file we just created to create new Kangaroos.
nickbenn (14:03:17): How old is each Kangaroo assumed to be, when it is created?
shirleybirdteach (14:03:24): 0
nickbenn (14:03:27): Yep!!
nickbenn (14:03:35): Do kangaroos of age 0 breed?
shirleybirdteach (14:03:42): hope not
nickbenn (14:03:54): Nope...even kangaroos of age 1 haven't reached anything close to full fertility.
nickbenn (14:04:04): So, we've got problems in our program.
nickbenn (14:04:16): But here's a question to end on, for today:
chtkjohn (14:04:55): what did I miss? the babies are all zero when born?
shirleybirdteach (14:05:04): yes
nickbenn (14:05:06): If we just looked at these numbers, what sorts of preliminary conclusions - about kangaroos, about our model, about our assumptions, about our program, etc. - might we reach?
nickbenn (14:05:11): Exactly.
nickbenn (14:06:20): That's it for today. Your assignment for today is as follows:
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chtkjohn (14:07:13): am i on
nickbenn (14:07:17): Post your answers to the above question in the WebCT Java forum; if you can't get on to WebCT, then e-mail them to me at
nickbenn (14:07:28): And there is a second question in the assignment:
pamrdoodle2002 (14:07:54): i didn't get the questions...had a problem with conference....
chtkjohn (14:08:23): me too
nickbenn (14:08:23): Without worrying about how we would write this in Java (i.e. write your speculations in English ), how should we fix the fact that all of the first batch of kangaroos in our Zoo program start out at zero years of age?
nickbenn (14:08:56): First question is: If we just looked at these numbers (that show the kangaroo population dwindling to nothing after a few years), what sorts of preliminary conclusions - about kangaroos, about our model, about our assumptions, about our program, etc. - might we reach?
nickbenn (14:09:47): if you can get on WebCT, post your speculative answers (there isn't a "right" answer) in the Java forum; if you can't connect to WebCT, email the answers to me, at
chtkjohn (14:10:40): ok now do we come back at 4 David to discuss abstracts?
challengebetsy (14:11:29): Nick, how about if we instructors conference about the abstracts at 3:45 - since you are holding an "office hour"?
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nickbenn (14:12:20): Sure thing, Betsy
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jkraloff2001 (14:13:13): Nick I was delayed getting on AND I still canoot get onto casbasa. Is there another way I can look at your java program assignment this afternoon without too much trouble?
nickbenn (14:13:13): You can find me on Yahoo IM, folks, for the next hour.
nickbenn (14:13:29): Actually, we did everything on mode.
jkraloff2001 (14:13:58): Nick - I am on mode now. Where are the files to look at/
nickbenn (14:14:14): copy the following:
nickbenn (14:14:19): orr, type the following:
chtkjohn (14:14:25): bye till 4
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nickbenn (14:15:29): cp /usr/local/scc/java/ .
nickbenn (14:15:37): cp /usr/local/scc/java/ .
nickbenn (14:16:25): compile both of them:
nickbenn (14:16:34): javac
nickbenn (14:16:38): javac
nickbenn (14:16:52): then run the Zoo class (which is a Java program):
nickbenn (14:16:57): java Zoo 100 10
nickbenn (14:17:20): that runs a simulation of a kangaroo population model, starting with 100 kangarroos, for 10 years.
nickbenn (14:18:38): (we made some changes to, but those changes are already in the copy you have; when I make this transcript available, you can see what those changes were)
nickbenn (14:19:47): After running it, answer the following questions (this is the assignment):
nickbenn (14:20:10): First question is: If we just looked at these numbers (that show the kangaroo population dwindling to nothing after a few years), what sorts of preliminary conclusions - about kangaroos, about our model, about our assumptions, about our program, etc. - might we reach?
nickbenn (14:20:26): Second question: Without worrying about how we would write this in Java (i.e. write your speculations in English), how should we fix the fact that all of the first batch of kangaroos in our Zoo program start out at zero years of age?
nickbenn (14:21:14): There are no "right" answers; I want your speculation. post your answers on WebCT, in the Java forum; if you can't connect to WebCT, then e-mail your answers to me at
jkraloff2001 (14:21:58): a very clear summary - thanks
nickbenn (14:22:28): You are welcome. I'll be posting the assignment (and my responses to it) on WebCT and the challenge/sti site.
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challengebetsy (14:26:48): Ok. I'm closing this conference in three minutes.
challengebetsy (14:27:44): OOps - I was not scrolled down and thought you were elsewhere, Nick - Not closing!
nickbenn (14:28:12): I'm here Not going anywhere.
challengebetsy (14:31:36): Although Dianne is listed on conference list, on Messenger list, it says she is not online.
nickbenn (14:32:33): That means she is invisible in IM (as I usually am)
nickbenn (14:33:21): What accounts (i.e. what directories on the mode web server) have the different teams' abstracts on them?
chidhkratzer (14:34:32): Go to and look at the bottom of the page.
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