Ever start at a new company and feel like the most difficult task is
just trying to figure out
the acronyms and nomenclature? If you're new to programming
there's going to be a lot of terms that you're not familiar with. Before we dive into this
Java course there is a few terms I want to make you familiar with.
In the Java videos I'm assuming that you don't know anything about Java
or how it works. If there's ever something unclear in the videos
feel free to post a question in the comments on DeegeU.com
or the Facebook group. I'm here to help you.
There's really only one goal for this tutorial. Get familiar with some of the
Java terms used in this tutorial.
In this lesson I want to introduce you to how Java works on your machine
why it works on multiple platforms and a few other miscellaneous terms
you should now.
Running a
Java program the same as running any other computer program
and some ways but in other ways it's very different. When you run a program
compiled through computer
you're running code compiled for your computer architecture.
A Mac will only run on a Mac, Windows will only run on Windows
and Linux only runs on Linux. One way we get around this
is by using a virtual machine. A virtual machine is a program that emulates the
behavior for a particular computer system.
The advantage is that you can compile once for a virtual machine
and your program runs any physical system the virtual machine can run on.
So we're taking code compiling it for a virtual machine
and any computer that can run the virtual machine can run your compiled code.
A virtual machine reads instructions from your program
and then translates it into instructions your computer can run.
When you write and compile a Java application
you're compiling it for a job a machine. Now
no one has a Java machine we all run Macs, Linux or Windows.
Java uses something called a Java Virtual Machine
Java Virtual Machine is also called by its initials JVM.
When you install Java on a computer you install a JVM.
Java applications you create are run on the JVM.
and this is how Java achieves platform independence. The basic development flow
for any Java program
will be to write the Java code into a text file compile the Java code into
class files
which are then fed a JVM. The JVM interprets the class file
into code your machine can understand. This is similar to any other compiled
programming language
When you download a virtual machine you're downloading
the Java Runtime Environment or JRE. The JRE contains libraries
and the JVM you need to run Java programs. The JRE does not however
contain what you need to write and debug
Java programs. For that you need the Java Development Kit.
Time for a quick history lesson.
Java has been around for a very long time. It was released in 1996. It was originally
called
the Java Development Kit. At least for the first two versions.
I've been using it since 1998 when Java 1.2 came out
and that's where it gets weird. 1.2 equals two.
That is Java 1.2 and Java 2 are the same thing.
I think it was a marketing thing but from that point forward in Java history
Java incremented by whole numbers and they changed the name.
It was now known as the Java 2 Standard Edition.
Later releases were also Java 2 even though it was really the
third and fourth or fourth and fifth depending on how you look at it.
The release numbers were 1.3 and 1.4.
Then came five. It was still Java 2 Standard Edition
but this version was 5.0. They added a ton of new functionality so
I think that's why they thought they should change the version numbers. Just in
case you're paying attention
they still reported it as version 1.5. The 5.0 was a marketing thing.
They just called it Java 5. Java 6 came out somebody finally noticed that hey
there still a two in the name
so they dropped the 2 and it became Java Standard Edition
It was the last major release by Sun Microsystems since they sold Java
to Oracle.
That was a pretty dark time for Java. People weren't sure what was going to happen to
the language.
Five years and many broken promises later, Oracle finally released a new
version of Java.
They added lots of cool features language like new file I/O code
but they also dropped a lot of things like lambdas.
And that brings us to the current version.
So why did we go through all the history of that?
The reason is, it gets very confusing what you're trying to use
for creating Java programs. JDK, Java Standard Edition,
J2SE. They're all the same thing. JDK is a superset
of the Java Runtime Environment, JRE. So you only need to download
JDK. If you need to install the Java Development Kit
on your machine searching for Java Download
might bring you to this page. This is not the download page you're looking for.
Move along!
This is just the JRE to run Java applications.
You want something looks more like this. This page was the download page when
Java 8
release 40 was latest and greatest. You can find the correct download for your
operating system here.
It may look different in the future, so if it does, just look for something similar.
If you think you're already have Java installed on your system
you can test that by typing Java dash version. You'll get a response similar to
what I have here.
Again the version numbers are wonky. If you see 1.8
you've got the right version. That is Java 8.
In this case it says Java 1.8.0
underscore 25. That means Java
release 25. Any release
newer than this should work for this tutorial.
The next concept to cover is Java keywords. Keywords are the words that are
reserved for the Java language. They are the words you use to write Java programs.
The list hasn't changed much since the language was created.
Each of these keywords is case sensitive. This means
they all use lower case letters and if you substitute a single capital letter
It will not be the key word anymore. Java is a case-sensitive language.
For example Boolean is not boolean.
The capital B makes it different. When we create variables and types later
you are strongly discouraged from using any these words with the different cases
for your identifier.
You can do it, but that's not a good idea.
I should note that true, false and null
are not really keywords. They're what's called literal values.
For example, "23" is a literal number. "true" is a literal boolean value.
We'll cover these more soon. They're included in the keyword list
of do not use for names, and that's why they're in there. Goto is a bit unique.
It's a keyword that's not used in the language. It's a silent jab at Microsoft
Visual Basic
and other languages that use goto in their language. Using goto is
considered
bad practice for most programs, so Sun Microsystems
made goto a keyword and then prevented anyone from ever using it.
The last important term to cover for now is the Java IDE.
IDE means integrated developer environment. The IDE is a nice slick user
interface that you use to create Java programs.
Java code files are ultimately text, but that doesn't mean you have to program in
textpad.
You can use whatever IDE you like. The most popular IDEs are
Eclipse and NetBeans. Both are free which is why they are so popular.
If you come from a Visual Studio or Xcode background
these IDEs are going to be a rough ride.
The IDEs are open source, and don't have the polish other IDEs have.
They're still light years better than typing programs
in Notepad. We'll use NetBeans in the videos
but there's nothing that we do use, that is particular to any IDE.
You're free to use Eclipse or NetBeans. Thanks for watching this video.
There is a quiz for this lesson on DeegeU.com if you'd like to gauge your
understanding of this lesson.
If you like the videos you're seeing, please let me know by liking the video and
subscribing to the DeegeU channel on YouTube. I'd really appreciate it!
If you have concerns or questions please leave them in the comments below, or
on DeegeU.com.
You can also let me know what topics you liked covered in future videos.
On DeegeU.com, there's a poll on the main page voting for the next
section of tutorials.
Thanks for watching!