String results = "";
for(char c: String.toCharArray()) {
results += (char)(c+3);
}

and

StringBuilder results = new StringBuilder();
for(char c: String.toCharArray()) {
results.append((char)(c+3));
}

He then proceeded to convert the entire collection of works by Shakespeare. Method 1 was estimated to take over 21 days by the computer. Method 2 finished in seconds. That caught my attention.
There are several cool data structures and search techniques that I have found awesome throughout this semester.

Binary Search

The people who write these algorithims are brilliant. To search through a sorted array, why look at every element? Why not just jump to the middle, see if what you are looking for is less than or greater than the middle, then do it again, with the new middle being the middle of the selected half.

ArrayList

ArrayList’s is essentially a circular array that handles the dirty details of dealing with arrays. When programming simple projects, I prefer to use ArrayLists as they are just more friendly than arrays. It dynamically resizes to allow you to constantly add without having to handle the actual details of expanding the underlying arrays. Finding an element at a certain element is VERY cheap as it essentially an array wrapper, the problem with ArrayList is removing or adding as it requires all of the following elements to be moved which can be pricey in a large array (I don’t mean hundreds, I mean hundreds of thousands).

LinkedList

LinkedList’s can be awesome when used correctly. A LinkedList is a group of nodes, linearly linked together. Node A contains certain data and a link to B. B contains data and a link to C, etc. This can be quite efficient if all you need to do is traverse the list in order. Finding a certain index can be much more costly than an ArrayList, but adding and removing at the end, or having a certain Node is extremely cheap. While sounding sort of lame, it can be very useful.

Tries

Now Trie’s really got my attention the first day of class. While looping through every String in a String[] can be very expensive, say an 80,000 word dictionary. While a binary search can cut that down to around 30 loops. Imagine if you could do that in 5 for a 5 letter word, or 8 for an 8 letter word. Imagine a tree, with the head having 26 children, each corresponding to a letter. From each letter are more children, and more children from there. Say following from the root, ‘a’ to ‘c’ to ‘e’, and ‘e’ contains a ‘emptyString’ property that holds the boolean true. You have found the word ‘ace’ in 3 actions. Mind boggling.

Conclusions

Knowing these staples of data structures enables you to mix and mash creating the perfect data structure for any ocassion. Today I mixed LinkedLists with float arrays to efficiently store millions of floating point numbers so that I could both stay memory efficient (arrays of primitive types) while keeping object sizes down (breaking the large arrays up through the LinkedLists). Note: I in no way claim to be a genius on this, or even know a good amount about it, as I have only spent a few months studying it, but it’s some awesome stuff that all developers should look into if they haven’t already.

• You often look up #apush, #aplang, #apphysics, #apcalc on Twitter just to see your fellow sufferers.
• You don’t think of it as “cheating”, you think of it as “cooperative learning.”
• You have multiple breakdowns throughout the year from school-related stress.
• On top of your full schedule, you’re involved in several extra-curricular activities and you have a job.
• Every extra-curricular activity you sign up for is framed with the words “It’ll look good for college.”
• You sign up for a class because it’s weighted, not because the subject interests you.
• You consider any non AP class to be a blow-off class.
• You never meet anyone new in your classes because its been the same group of kids since ninth grade.
• You and your closest friends are all in the top 10% of your class.
• The probablity of your homework getting done depends more on your mood than the fact that it needs to be done.
• You consider anything below a A to be a bad grade.
• You watch TV or do other random things until 10pm then complain the next day about doing homework at 2am.
• You find yourself complaining to everyone how much homework you have… when you should be off facebook doing it.
• You get mad when non-AP students whine about how much homework they have.
• Sometimes the highlight of your life is just crawling into bed and passing out.
• You use random, obscure information you learned in class in everyday conversation.
• You stare at your homework and repeat the words FML as you go through it.
• You know that school is a joke after the second week in May.
• You write BS-ays instead of essays.
• You have back problems because your backpack weighs more than 50lbs.
• You can’t help but find symbolism in every single thing you read/watch.
• Sparknotes is practically your homepage.
• You can’t have a conversation with your friends without mentioning homework at least once.
• You’re actually disappointed because you realize that you could’ve gotten a lot more AP classes into your high school transcript if they’d let you start as a freshman.
• You look at your AP results to cheer yourself up when depressed about your lack of a social life.
• You are annoyed after the ap test because it was SO much easier than all the practice tests and you didn’t need to have studied THAT much.

So I need to verify it, the main and recommended way is to use TXT record supported by most domain name registrars. Well mine wasn’t supported. Shouldn’t be a problem, all I need to do is upload an HTML file to a server behind the domain name to verify. That is quite dificult it turns out.

Next I fire up a VM, put a web server on it, put the verification file on it, and open it to the world and put it in the DNS settings for the domain name. Cox Communications doesn’t allow port 80; FAIL.

Try two, I’ll do a redirect from my domain name to a file on jtmcgee.net projects. FAIL, Google Apps doesn’t allow redirects when looking for the verification file.

3rd times the charm, right? I’ll CNAME my App Engine and put my project there. FAIL, the App Engine just redirects me to google.com.

4th time I try to CNAME my own website. This has a similar result, getting redirected back to epicserve.com, the owner of the servers website.

5th time, I contacted my friend Brent and asked him to work some config magic so that I could CNAME my project server without redirecting. Finally I can validate!

Yet I am still waiting for that CNAME change to propogate to the DNS servers around the world… 1and1 is famous for their slowness. It shows up right on my computer I am just waiting for it to show up right at Google.

Never thought something so simple would take so long.

The Happy Birthday Facebook App was designed for lazy people, me in mind, that want to post on peoples walls at midnight for their birthday so it can be special and all, but for one reason or another they can’t. This app basically lets you choose friends to wish happy birthday to at midnight, set a custom message, and adds it to the database to wait for that special night when it strikes 12. Then it will use that access token you gave it long ago and write on their birthday giving them your special message.

Like a large majority of my projects, it is open sourced.  You can find it at GitHub and do whatever you want with the source. If you are looking for a simple Java Facebook app example or a simple Java App Engine app example, then it’s for you.

Try it out on Facebook.

This year I moved the project to GitHub and you can find it here. This years version features an install script that dramatically makes it simpler to setup. Once you clone the git repository just running the install.php will setup everything from the MySQL DB, to error reporting, to your Google Maps API (for the map on the geo-location). All that’s needed to install this correctly is giving the web server the ability to write/edit files.

If you have a plugin for eclipse that you release check it out. Worst case scenario is it breaks, and if that happens it will turn itself off, stop logging, and allow the downloads to continue as if it was never there. Check it out.

On my new laptop I got a few days ago (Intel Core 2 Duo 2.2 ghz, 3 gb. ram, Latitude D630 w/ docking station, 14.1″), I first started by heeding the advice of my favorite blog, Lifehacker. I love Lifehacker, I have wallpaper for it, get emails daily with posts in it, read it daily on their website, follow it on Twitter, Liked it on Facebook, have it’s RSS on my iPod Touch, simply I like it a lot. Anyways, for a long time they have recommended LastPass as a great way of providing better security for your passwords. For a long time, I didn’t want to do it because I always thought it was important that I knew the passwords to all the places I used, and that if I was using a school computer or something, I wouldn’t be able to get the password. Well, I learned the cool part about LastPass is that it is stored online, making your passwords and other secure data accessible from anywhere, and providing syncing of passwords across browsers and OS’s. When I set it up, it was kinda scary cause it could see the passwords Firefox and Chrome had been storing, and the plain text of the password, which alone made it enough to convert and give up basic password managers. LastPass has some really cool login methods you can use, ranging from a printout grid that you have to input random parts from to having to have a certain USB drive plugged in to log into the website. I just use the simple log in method as I cannot guarantee myself that I will have one of those methods on me at all times. Another cool part about LastPass is its random password generators, I feel safe now knowing that all my online accounts have unique 12 character complex passwords, and the best part, I don’t know them. In short, I am a believer  in LastPass now in just about two days.

My second thought was, I still have information I don’t want losing on my PC besides just my laptop and for that I installed another Lifehacker recommendation, TrueCrypt. TrueCrypt has a lot of options for doing whatever you wanted, but what I wanted was a total OS encryption, before Windows can even boot, it must have my passphrase for decrypting the drive. I have not really seen that much of a slow down so far, and from what I read as long as you use AES encryption (DoD standard) you shouldn’t. *Random sidenote: In NCIS the forensics scientist Abby once talked about how to truly delete data you must write over the specific part of the hard drive several times, with TrueCrypt I was able to select that option when it encrypted, it wiped 3x to remove any traces*

And lastly, I added a double backup on my laptop (hadn’t set it up yet, only had it about a week or two), one backup to my local server, and one to my 2 TB. external hard drive.

I now feel fairly confident in the security I have put on my laptop (and desktop as my /home directory has always been LUKS encrypted, backed up, and now LastPass) and that I can deter most thieves from my data and the ones smart enough that get it won’t really be interested in what is on a 16 year olds laptop. If you haven’t taken at least one or two of these security measures, I recommend you do.

Introduction to Working with Facebook

When writting my application, it happened to be a canvas app, or it was accessed via apps.facebook.com with a iframe to my acctual app. When I would get a new user I would immediatley get a new cookie that was named fbs_APPID within this cookie, most importantly, there was a access token. Now to know any information about a user, one must have one thing, an OAuth access token.

Getting an OAuth access token

Most times you will have a token in the cookies, however on some random times that I never figured out the pattern to, you just don’t have that information there. And as for most apps, you need to know some information about a user, and possibly even post or something of the like with the users permission. However, for protection, Facebook just doesn’t allow any application developer access to their entire database. So to allow only certain access to certain applications, applications are given OAuth tokens, these tokens are user specificic and generally session specific. With these tokens, you could use the later discussed Facebook Graph to get just about any needed data.
The process of getting an OAuth token if it is not in the “fbs_” cookie can be quite strenuous. First you need to redirect the user to the Graph server with certain application-specific parameters. Next, one of the parameters happened to be a call back url, now that url is called and Facebook gives you a code. Using this code and your application secret you can finally get a new OAuth access token. Basically what all these redirects does is allow Facebook to check that this user is acctually logged in and that this user is allowing the application access to this information.

The Facebook Graph

Why they call it the “Graph” I am not quite sure, however it is quite a handy tool. Just heading over to http://graph.facebook.com/me will provide you some basic information about yourself, provided that you are currently logged into Facebook on that browser. Furthermore looking up more information is easy, all you need to know about something is it’s Facebook ID. Everything on Facebook has an ID, from an event to a group, to a person. With people you can even use words like the ones that are for your profile. You can access some basic information on me by going to http://graph.facebook.com/jordan.deloach.
Want other information? It’s easy

• http://graph.facebook.com/me/picture links to that select person’s profile (replace Me with the FB ID of anything on Facebook)
• http://graph.facebook.com/me/home Your news feed
• http://graph.facebook.com/me/feed Your wall
• http://graph.facebook.com/me/movies Your movies.

Obviously there are many more than this, and it as simple as fetching these url’s in your application to get all this data. Check out the Graph API for more examples and the nitty-gritty syntax. You can get all sorts of data on any event, photo, anything really.

Where these two technologies meet

Now the reason that we discussed OAuth tokens was that so you had them in your application for when the time came when you needed some data. Not all data requires a token, in fact any data visible by outside (non-friend) users is visible. However when that no longer cuts it, an access token with proper permissions can get you all the data you need. When applying the access token it is as simple as putting it as a GET argument

https://graph.facebook.com/me/friends?access_token=w5h2kl5jhkleh235hjkl23h5jkwhfklq3

Note: when using an access token you must use HTTPS or a secure connection.

Another note: Me refers to the user who authorized the access token, not the developer.

And another, major note: all data will be returned in JSON Object forrm, so all you need is a few libraries, or if they are included with your language you’re fine.
For Java I used the libraries are JSON.org, they worked just fine.

Now for this application, as I wrote it in a matter of days and released it the day of schedule releases, I had to go with a language I knew very well, and I had to have a reliable, dependable source to host it at. I automatically though of the Google App Engine as it is pretty sweet to play around with and now would be a great time to test it in a live environment. My previous application I had wrote on Google’s free, scalable engine was written in Python. It utilized the amazing Django framework, but I felt like I didn’t really understand the Python language as well as some others. The only other option for selection on the App Engine was Java. This was perfect as I had just completed a summer class on Java and it was extremely fresh in my mind.

Core Java Servlets

Now coming from PHP for web development the idea of Servlets and JSP’s was totally a different way of thinking. With PHP I was used to putting what code I needed to on each page to achieve what needed to be done. With a bit of Python/Django experience, Java’s way was still different, but not as different as PHP to Java. Java’s JSP method reminded me a lot of Django templates, except that JSP’s are a load more powerful. As Django templates (at least from my experience) only allow a few tags, a JSP allows practically any Java code (that would normally go inside a main method) and allows imports and special features unique to JSP’s, like includes. JSP’s includes in fact reminded me some more of Django’s templates with all the splitting up possible of the HTML files.

Now that we briefly know what a JSP is, a servlet is just like a Java class that implements the standard Apache servlet. Within these servlets you have two methods by default doGet(HttpServletRequest req, HttpServletResponse resp) and doPost() with the same arguments. There are a few differences from a standard Java class beyond those previously noted:

resp.getWriter().println(); // to print to the screen you must get the PrintWriter via the resp.getWriter() method
resp.setContentType("text/html"); // must do if you print out any HTML and don't want it to appear as standard text
resp.sendRedirect(String url); // a simple way to send a user to be redirected

There is (obviously) no console input on a web browser, so the standard way to get input via the web is through GET and POST methods. These are handled via the corresponding doGet() and doPost() methods. Now to actually get the value passed, you must know the variable name and use it accordingly.

req.getParameter(String paramName); // where paramName is the ?name=Joe&age=18 name or age

Sometimes you will also find yourself in need of getting an array, from say a multiple choice drop down.

req.getParameterValues(String paramName); // just once and it will return a String[]

Now onto more of the theory behind servlets, and less of the syntax. Now please remember when I say theory, this is just the way I perceive it. In my application if I would have a full blown HTML page, I would always put it in a JSP as it is so simple and better looking. However when there was a simpler page that had a bit more code behind it, I would make that a servlet. An example of a simpler page with more code that I used as a servlet would be my form handlers (any adding or updating interaction with the database), and also I handled the OAuth authentication with servlets.

JSP’s

JSP’s, or Java Server Pages, are a mix between Java code & client-side scripting. It allows you to mix the power of Java and your the models in your MVC framework with the simplicity of a HTML file. You probably see them all over the web, as they are quite effective, especially in larger businesses and universities.
I have not personally gone that far into all the powers of JSP’s but enough to know that I like them. I am not going to try and write a tutorial but just point out a few things I use and a good tutorial or two.
Now one of the simplest, but greatest is the server-side include of static content. This allows you to keep your web pages on the server side leaner and able to easily change base things like headers or footers.

<%@ include file="/include.html" %>

Other useful things to know, if you need to get any parameters or need to mess with the request or response, they are simply called request and response in all JSP’s. So you could use a request.getParameter("id"); for example.
If you need to write anything to the page from within the Java code just throw a out.println(String value); or out.print(String value).

For anything more than what I included check Google for some JSP tutorials or here is a good looking one.

Benefits

I see there being several benefits of using Java as the language behind more complex applications because of it is an object oriented language. It being OO allows code to get so many more times complex. Now, in web development at least, a OO language is only as good as the database that supports it . I happened to be very lucky with Google App Engine as it was powered by a OO database allowing me to store some of my unique data types like “Student”, “Teacher”, “Course”, and “Schedule” in the database and retrieve it like it has been open since it was created. Most of the interface for this was provided in the JDO classes in javax.JDO.
With this and a few classes for getting and selecting certain Students/Teachers/Courses, it was very easy to get exactly the results I want in a few lines of code in a JSP. And I know that in Python and PHP you can have classes and objects, but it’s just not the same as it is in Java. While Java can be pretty strict with it’s types and defining them, it in turn gives a lot of power to create awesome and dynamic applications for the end user.

Finally

As I have been reading in my “Clean Code” book, it is better to take longer and write software better the first time. Better being Javadoc’d and Object-Oriented. If you were to write it the other way, with say PHP or Python and have each script access the relational database, get the results, sort the results into the data you need, and output it correctly, that is so much code duplication. One script could be anywhere from 20% – 50% of the same code over and over, why not just write it great in the beginning in an OO way so the only code duplication you have is one or two lines to load the pre-written-by-you libraries that does all that work in one place, one time.

And sorry Brent I think I like Java Servlets & JSP’s a wee bit more than Python/Django even though I think Django is a great framework and would love if it were written in Java instead, Python just isn’t as big and powerful as Java.

My application, only available for MHS students, allows you to add your schedule (teachers and classes), see who’s in your class, comment and Facebook Like both your teachers and your hours.

It was written on the Google App engine, using an OO (object oriented) database with JSP’s and Core-servlets. I  will be writing a post about this stuff later.

For some who want to complain about how “bad” it is, I remind you this was about 8 days of work. However here is some of my attached code for it. Note: this is only SOME, not all.

socialschedulesSource [zip]

I do not see the “Hello World” that intimidating anymore, for the single reason is that I know what and why all those words are there at the beginning of the file, and the best way for you to get into it is to understand it.

public class HelloWorld {

    public static void main(String[] args) {

        System.out.println("Hello World");

    }

}

The first line is public class HelloWorld. public simply means that from anywhere and by anybody this class can be called. The class simply means that it is a class, as all beginning files in Java will be. The HelloWorld I think should be pretty easy to understand. The second line, public static void main(String[] args)... is a bit more complicated. The public meaning that this method can be called from outside this class. static means that this method can be called without initializing the whole class as an object. void simply means that it returns no value, as methods in the future might, like int or boolean. The next part, main means that this method should be run whenever this program is run, for any Java program to run, there must be a main method. String[] args is probably the strangest part, String is a line of characters, like a word, sentence, anything really. In Java, this [] mean an array, so String[] args means that for it’s parameters it takes an array of Strings. However you won’t deal with this for a while in your Java career. System.out.println... breaks down to System, which is a package (a folder full of classes) and out is a class within the package that deals with output. Finally println is a method (function) which prints the line.

Understanding Strings

Ever wondered why in Java, you see things like int and double and they are lower-cased, but String is capitalized? All class names in Java are capitalized, and so must String be.

String myname = "Jordan";

You are creating a new object (unique version of a class) of the class String. With strings you can do so much more than a primitive type (int, boolean, short, etc.). As myname is an object, it has methods that uniquely work with it.

System.out.print(myname.length()); // prints number of chars in myname

System.out.print(myname.charAt(4)); // prints ‘a' for the 5th char in it

There are many more options, but that will do for examples of how this is an amazing way to store Strings.

More on Classes and Objects

To help you differentiate between classes and objects, I offer the following example.

MathOps.factorial(5); // uses the class MathOps and static method factorial()

MathOps math = new MathOps();

math.factorial(5); // uses the unique object

// another example that shows benefits

ShoppingCart cart1 = new ShoppingCart();

ShoppingCart cart2 = new ShoppingCart();

cart1.add("blanket");

cart1.add("shampoo");

cart2.add("ice cream");

cart1.remove("shampoo");

System.out.println(cart1.list());

System.out.println(cart2.list());

Yes, I have not actually made any of those classes, but those were just for examples, see with the ShoppingCart example, you saw exactly the benefits of the different objects as opposed to storing them in one big class where it would get all mixed up together.

User Input & Reading Files

It is quite strange, but in Java these are EXTREMELY similar so they shall be grouped together. To read user input in Java, one must first look for it.

Scanner s = new Scanner(System.in);

Scanner is a great class. I used to oppose it, but now seeing it’s virsitility, it’s a great class. Anyways what this says is create a new object named “s” that reads System input. To get a line of input is as easy as s.nextLine();

System.out.print("Please enter your name: ");

String name = s.nextLine();

System.out.println("Hello " + name);

Now the reason it was grouped with reading files is because if you want to ready a file, just tell Scanner so.

Scanner s = new Scanner(new File("filename.txt"));

while(s.hasNext()) { // hasNext() returns true as long is there more lines

    System.out.println(s.nextLine());

}

That would print out every line of the file. It is just like reading input, just a different start.

Loops and If’s

If your familiar with PHP this is extremely easy and only requires a paragraph or two.

boolean a  = true;

if(a) {

    // then do this

} else if(!a) {

    // then do this, notice the space between else and if not elseif

} else {

    // else do this

}

if(a) {

    // one line only can use this format

} else {

    // same for loops too

}

for(int i = 0; i < 10; i++) // you can use {} if you want

    System.out.println(i);

while(true) {

    // infinite loop

}

Good Things to Know

Integer.parseInt("123"); // can take a string (like user input) and convert it

Double.parseDouble("2.3"); //ditto

String b = "hey";

b.charAt(0); // gets the a (parameter) character from a string

Conclusion

With just that basic two to three page intro, you should be pretty set. Using just the things desribed here, you can do just about anything text-based. If you want to start working with GUI’s you’ll have to go to google and find a nice tutorial on how to do that. It’s more work, but it is just an extension of this sort of thing.

Glossary

Method (Java) ~ Function (PHP)

Int ~ Medium ranged integers

Double ~ For numbers with a decimal

Boolean ~ True or false