One of the difficult things about getting started with Java is installing everything you need. Even before you write a single line of code, the headaches begin! Hopefully, the following sections will make life easier for you.
We're going to write all our code using
a free piece of software called NetBeans. This is one of the most
popular IDEs (Interface Development Environment) in the world for
writing Java programmes. You'll see what it looks like shortly. But
before NetBeans will work, it needs you to install the necessary Java
components and files. First up is something called the Java Virtual
Machine.
The Java Virtual Machine
Java is platform independent. This
means that it will run on just about any operating system. So
whether your computer runs Windows, Linux, Mac OS, it's all the same
to Java! The reason it can run on any operating system is because
of the Java Virtual Machine. The Virtual Machine is a programme that
processes all your code correctly. So you need to install this
programme (Virtual Machine) before you can run any Java code.
Java is owned by a company called Sun Microsystems, so
you need to head over to Sun's website to get the Java Virtual
Machine, also known as the Java Runtime Environment (JRE). Try this
page first:
You can check to see if you already
have the JRE on your computer by clicking the link "Do I have
Java?". You'll find this link under the big Download button at the
top of the page. (Unless Sun have changed things around, again!)
When you click the link, your computer will be scanned for the JRE. You
will then be told whether you have it or not. If not, you'll be
given the opportunity to download and install it.
Or you could just head over to this page:The "manual" in the above links means "manual download". The page gives you download links and instructions for a wide variety of operating systems.
After downloading and installing, you may need to restart you computer. When you do, you will have the Java Virtual Machine.
The Java Software Development Kit
At this stage, you still can't write
any programmes. The only thing you've done is to install software so
that Java programmes can be run on your computer. To write code and
test it out, you need something called a Software Development kit.
Java's Software Development Kit can currently be downloaded from here:
The one we're going to be using is
called Java SE. (The SE stands for Standard Edition.). Click on that
link, then on "Java SE (JDK) 6 Download". You'll then find yourself
on a page with a bewildering list of options to download. Because
we're going to be using NetBeans, locate this:
JDK 6 Update X with NetBeans 6.x
Click the Download link to be taken to
yet another page. Click the top download to be taken to a page that
asks you to select your operating system. Click Continue to finally
get the download you need. A word of warning, though - this download
will be big, at over a 130 megabytes at the time of writing! Once
you've downloaded the JDK and NetBeans, install it on your computer.
We're going to be using NetBeans to
write our code. Before launching the software, however, here's how
things work in the world of Java.
How things work in Java
You write the actual code for your
programmes in a text editor. (In NetBeans, there's a special area
for you to write code.) The code is called source code, and is saved
with the file extension .java. A programme called Javac is then
used to turn the source code into Java Byte Code. This is known as
compiling. After Javac has finished compiling the Java Byte Code, it
creates a new file with the extension .class. (At least, it does if
no errors are detected.) Once the class file has been created, it
can be run on the Java Virtual Machine. So:
- Create source code with the extension .java
- Use Javac to create (compile) a file ending in .class
- Run the compiled class
NetBeans handles all the creating and
compiling for you. Behind the scenes, though, it takes your sources
code and creates the java file. It will launch Javac and compile the
class file. NetBeans can then run your programme inside its own
software. This saves you the hassle of opening up a terminal window
and typing long strings of commands,
Now that you have a general idea of how
Java works, launch your NetBeans software. Then click the link
below to go to continue with the lesson
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