Monday, 14 March 2016

Static vs Non-static in Java

A really good (and tough!) distinction that everyone coding in Java needs to know: the difference between static and non-static variables in Java.

In my opinion, tutorial4us did a great job explaining it. A very good read indeed.

My understanding is that instance (non-static) variables exist in each object (instance of the class). Each object will have its own value/content for each instance variable. Think of the name in a Person class. We define the name as an attribute or property of a person, and each Person object will have its own name.

Static variables exist only inside the class where they are declared. Some call them "class variables" because they are bound to the class, not the object. They are unique and when a new object is instantiated, the object does not get its own copy of it. Rather than using the dot notation with the object (object.nnnn), you would use it with the class (Class.nnnn).

Note that this also applies to, and is also often used with methods!

Think about these example:

public class Test
  public static void main (String args[])
    int[] numbers = {1,2,3,4,5};
    System.out.println( numbers.length ); // =5
    // length (size/number of elements) of the array object
    System.out.println( Math.PI );
    // PI is stored as a static constant inside the Math class
    // we don't need to instantiate a Math object to use PI

To code or not to code

...For some of us, that is the question!

One of my favourite authors, V. Anton Spraul, has an interesting website about his books, programming, computer science, and other topics.

What caught my attention (this time) is the Learning How to Program: A Guide section of his web site.

I would like to recommend reading part two, "How do I know if programming is for me?" to anyone considering a CS course, diploma or degree, job, or anything that involves coding.

Below are my favourite quotes from the points he makes:

  • "A good programmer enjoys programming. I don't mean that every act of coding will bring unbridled joy, or that programming is fun in the same way that playing a favorite sport or video game is fun. But there should be a real pleasure in seeing one's program working, even if the program is a pitiable little thing that accomplishes almost nothing."
  • "Probably just about anybody could become a pretty good programmer if they work hard enough to become one. But make no mistake about it, programming is tough mental work. If, on some level, you're not enjoying the work, you're never going to be able to focus on it long enough to master it."
  • "Unfortunately, just because a person really enjoys working with computers doesn't mean he or she will enjoy programming. I guess the reverse is true, though; if you don't like technology, you probably shouldn't try to learn programming."
I couldn't have put it better myself. Thanks again, Mr. Spraul.

Thursday, 3 March 2016

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:

Memory and Storage Devices

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