<p>Oh. Never thought of it that way, thanks. SO it has the best of both worlds.</p>
<p>Yes, but you have to cast myTruck to a Truck each time you want to use the methods unique to the Truck class (assuming the declaration myTruck = new Car(); never took place)</p>
<p>Wait, so what determines if the object can use methods is what is on LEFT of the = sign, correct? Then what is the RIGHT of the = sign used for…?</p>
<p>And sorry, but another question came up. Can you add an element to a string above the size? For example, a string has a size of 3. Can you do string.add(string.length(), x), or will an oout of bounds occur?</p>
<p>Not sure what you mean, but I think the right is the type of reference, and the left is the object it is initialized as. You still need to cast if it is a different reference type though to access the unique methods.</p>
<p>and i am not aware of any add method in the string class…</p>
<p>I feel pretty confident for APCS. I took the first practice test in Barron’s, and the multiple-choice is definitely harder than 2009 released exam, IMO. I was always making mistakes on the actual M/C, though.</p>
<p>I’ve also printed out every FRQ since 2004 and worked through them. If you haven’t done that, you should. It really helps (at least that’s the way I feel).</p>
<p>@aryus: I don’t think the add() method for a String exists.</p>
<p>I’m sorry, i meant ArrayLists. Let me rephrase the question, if you will:</p>
<p>Wait, so what determines if the object can use methods is what is on LEFT of the = sign, correct? Then what is the RIGHT of the = sign used for…?</p>
<p>And sorry, but another question came up. Can you add an element to a ArrayList above the size? For example, an ArrayList named list has a size of 3. Can you do list.add(.length(), x), or will an out of bounds occur?</p>
<p>@Kalathalan: Can you send me the link to the 2009 released exam (though I may have already taken it). Yes, I’m currently looking thru the FRQs, and they are not that difficult IMO, not anything compared to the MC…</p>
<p>@aryus: Sorry, I don’t have it. We took the exam in class and our teacher made us give it back after we looked it over.</p>
<p>I’m not sure what the answer to your first question is…</p>
<p>Yes! ArrayLists can expand to any size, unlike regular arrays. When adding an element, you can specify a position explicitly: list.add(3, x), or just add it to the end: list.add(x). An out of bounds error will not occur. If you call list.add(3, x) and something already exists at 3, everything moves up one index and list.get(3) becomes x.</p>
<p>Remember that you get the size with list.size() and that the last index in the ArrayList is list.size()-1. :)</p>
<p>I’m seriously freaking out. I can barely get over 10 points on the FRQs… I just hope the curve is really more lenient!
Oh and also, that’s not the only new stuff from AB.
<a href=“Supporting Students from Day One to Exam Day – AP Central | College Board”>Supporting Students from Day One to Exam Day – AP Central | College Board;
Page eight. But come to think of it, that’s not really much at all…</p>
<p>And can anybody at least post part of an official question (2004/2009)?</p>
<p>Sorry I’m double posting guys, but can somebody explain when exactly a nullpointerexception occurs?</p>
<p>a NullPointerException happens when a method call for an object of a class tries to access a null reference… also you need to initialize reference instance variables in the class or the compiler will set them to null</p>
<p>I’ve been gradually studying for two weeks. All I really need to do now is cram GridWorld tonight. I got a 31/40 on the MC on the Barron’s test I took but it was untimed and I took a ton of time flipping back to the GridWorld methods documentation (which is why I need to study it!)</p>
<p>Also, I took the class last year and haven’t done any Java programming since, but I’ve done a lot in other languages so I can understand what’s going on in the code easily enough. But I’m afraid I’ll forget some Java peculiarities when I get to the FRQs and get points off. Does anyone know how they approach grading the FRQs?</p>
<p>The best thing for you would be to just go through a couple of them on collegeboard’s official site. </p>
<p>And for the love of God, can anyone please tell me what’s the freakin’ difference between abstract classes and interfaces. -_-</p>
<p>I got a 38/40 on the 2009 official multiple choice. But I got a 31.25 on Barron’s, so not sure if that means I got lucky on the first one or if Barron’s is just harder.</p>
<p>Meanwhile, I just can’t do the FRQs. How many points on the FRQs are free points/points for doing trivial stuff? I need those.</p>
<p>^
Can you please post the link to the 2009 MC?</p>
<p>I thought that Barrons would be easier for the comp Sci, but hopefully it isn’t.</p>
<p>I consistently get 30-33/40 on the MC, missing 4/5 of the gridworld (need to study it) and some other ones that I wasn’t sure about.</p>
<p>You can use == with Strings, but only if the Strings are both declared like:</p>
<p>str1 = “hi”;
str2 = “hi”;</p>
<p>or</p>
<p>str1 = “hi”;
str2= str1;</p>
<p>I, thought that it was you either had to use .equals() all the time or you could use == all the time because that was almost a year ago when I learned this stuff, but it is good to clear that up. It is annoying to treat it like an object and primitive, but at least it is clear now.</p>
<p>The only FRQ that I hate are the gridworld one, because everytime I’ve taken the test I haven’t had any reference to any gridworld information.</p>
<p>I was wondering would a reference to the gridworld classes be provided on the exam? Or should I just study for that all now (My H0)?</p>
<p>Thanks.</p>
<p>^
You are given a reference to all of the GridWorld classes and methods.
Still, study them so you are familiar with them.</p>
<p>Thanks.</p>
<p>During my practice FRQ, when I got to the gridworld I had to start making up methods that sounded like they did the right thing. </p>
<p>I’m going to make a study guide with all of the things I missed + gridworld and hopefully that will help.</p>
<p><a href=“Supporting Students from Day One to Exam Day – AP Central | College Board”>Supporting Students from Day One to Exam Day – AP Central | College Board;
You get this quick reference on the test. You should try getting used to it so that it’s not a whole new thing on the real deal.</p>
<p>For those of us taking it tomorrow, this was posted on the Cram Packets thread, but I’ll just link it to here. </p>
<p>It’s a pretty good study guide: It’s under Computer Science <a href=“http://talk.collegeconfidential.com/ap-tests-preparation/921322-ap-cram-packets-list-yours-here-3.html[/url]”>http://talk.collegeconfidential.com/ap-tests-preparation/921322-ap-cram-packets-list-yours-here-3.html</a></p>
<p>Thank you. That will make this so much easier.</p>
<p>Do we get that for the MC or only the FRQ?</p>
<p>Thanks.</p>