this Java keyword

A feature of Java that usually confuses beginners is the "this" prefix.

In a nutshell, the this keyword is used to distinguish between parameters of a method and attributes (instance variables) of a class.

The following link will lead you to a web page that does a great job contrasting and explaining this with examples:

• http://www.javatpoint.com/this-keyword

Distribute your Java classes in a JAR file

The source of the information given in this post is http://www.skylit.com/javamethods/faqs/createjar.html
In my opinion, the simplest and quickest way to do this is using the command line.

Steps

1. Start the Command Prompt. The easiest way is to Shift-Right Click on an empty spot in your Windows (File) Explorer. Make sure no files are selected, though. The idea is that your Windows Explorer should be in the location of your Java files.
2. Navigate to the folder that holds your class files:
   Copy the path from Windows Explorer's address bar (more details about WE here), then type the following into the command prompt window:
   cd /d 
3. minding the space at the end, then paste the path that you copied from Windows Explorer's address bar. Press Enter.
4. If you haven't set your path to include JDK’s binaries (compiler and utilities, including the one that creates jar files), you need to do so by adding it to your default path (your folder may differ depending on the version of the JDK that you installed)
   path %path%;C:\Program Files\Java\jdk1.8.0_83\bin
5. Compile your class(es):
   javac *.java
6. Create a manifest file and your jar file (Replace IA with the relevant name to your project):
   echo Main-Class: IA > manifest.txt
   jar cvfm IA.jar manifest.txt *.class
   ---- or ----
   jar cvfe IA.jar IA *.class
7. Test your jar:
   java -jar IA.jar
8. Create a batch file so your end user can double click on it to run your command line application (you may also use Notepad to do this):
   copy con run.bat    (creates the file)
   java -jar IA.jar    (Press CONTROL Z and Enter to finish and save the file)
9. Double click on run.bat to test it.

IBDP Computer Science IA

Important information about the

IBDP Computer Science Internal Assessment

Screencasting & File Requirements

Mac:

• http://digitalwriting101.net/content/how-to-make-a-screencast-with-quicktime-x-for-mac/

Windows:

• http://readwrite.com/2015/05/26/screencasting-windows-pc

Ensure that your screencast is about 5 minutes long, and in MP4, MOV, M4V format;
Maximum size 500 MB

Formatting of work for IBDP Computer Science IA

• Arial font size 12 (where the language / script supports it)
• Double-line spacing
• Numbered pages
• Portrait orientation (rather than landscape) – except where it is necessary to accommodate a specific item such as a graph or illustration
• DOC, DOCX, PDF or RTF

Java Scanner class confusion

If you have used Java's Scanner class, yopu may have come across an odd behaviour as you use the same Scanner object to input numbers and Strings.
I recently found the best explanation for this behaviour (it's not a bug), which you may find and here here at Daniweb. The best replies are from cgeier and BestJewSinceJC

---

The reason it gives you trouble is because when the user enters an integer then hits enter, two things have just been entered - the integer and a "newline" which is \n. The method you are calling, "nextInt", only reads in the integer, which leaves the newline in the input stream. But calling nextLine() does read in newlines, which is why you had to call nextLine() before your code would work. You could have also called next(), which would also have read in the newline. (BestJewSinceJC)

---

Just change the delimiter.

Scanner in = new Scanner(System.in);
in.useDelimiter("\n");

(cgeier)

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Hope you find these useful.

What is usability?

I have been looking for useful definitions of usability within the context of Computer Science.

I'll update this post as I find more and better resources.

• http://www.usabilityfirst.com/glossary/usability/
• https://msdn.microsoft.com/en-us/library/ms997577.aspx

Binary Search Trees

Best Links to Revise: Binary Search Trees (BSTs)

• http://visualgo.net/bst.html - animated binary search trees (BSTs)
• http://www.algolist.net/Data_structures/Binary_search_tree
• http://www.geeksforgeeks.org/618/ - BST traversals
• A great wikibook for A Level Computing including the best way to learn BST traversals
• http://www.cs.swarthmore.edu/~newhall/unixhelp/Java_bst.pdf - slideshow on BSTs
• https://www.cs.rochester.edu/~gildea/csc282/slides/C12-bst.pdf - more slides on BSTs; recommended to read up to and including the topic on deleting a node from a BST
• Trees and tree algorithms from the interactivepython.org

Java programming

Just a couple of great online resources on Java programming:

• http://howtodoinjava.com/2013/06/07/5-class-design-principles-solid-in-java/
• http://www.ntu.edu.sg/home/ehchua/programming/
• http://introcs.cs.princeton.edu/java/home/
• http://nclass.sourceforge.net/downloads.html

Hope this helps!