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Installing Eclipse

You will be using a program called Eclipse to write Java in. Eclipse is an example of an IDE, which stands for Integrated Development Environment. In short, an IDE is an application which contains a set of tools used to create programs in whichever language you are using. The IDE will constantly check to see if the syntax of your code is correct and that you have not made any silly mistakes. So, you can imagine the IDE as being an English teacher who is constantly checking to see if your grammar/punctuation (syntax) is correct whilst you write sentences, or in our case, code. As the IDE is running all the time, if you are typing in code and you have not yet finished writing the line you may encounter errors and your code may be underlined in red. This is nothing to worry about and will only be a problem when you finish writing the line, at which point you need to do some investigative work. Try to see if you have made a silly mistake, and if that endeavour bears no fruit, read the error and try to understand what it is trying to tell you, and then correct the mistake. This process of finding and eliminating errors is known as debugging.

So now we will cover how to install Eclipse:

First, head over to Eclipse's website, which looks like this:

A screenshot of the Eclipse website front page

Next, search in the searchbox for Eclipse standard:

A screenshot of the results

Now click Eclipse standard 4.4, the first one listed:

Eclipse standard 4.4

Now under download links, you should see your OS (Operating System). Click it:

Know your computer version

Next, click where it says [United Kingdom] UK Mirror Service (http), or do the same for whichever country you are in:

This was made in the UK

Now save the file. Once it has finished downloading, open and extract it.

Now simply double click on the eclipse file and Eclipse will now open.

What this course entails

In this course you will learn how to program in Java and then Swing. You can think of programming as a way of making your computer do things - and anything that you create and run on your computer is called a program. Programs can be seen as a set of instructions that get executed when you run the program. The instructions for programs cannot be written in plain English; they must be written in different languages, one of which is Java. Anything you write in Java is called code, and lines of code look very similar to sentences. However there are some key differences, such as that lines of code end in a semi-colon (;) not a full-stop. Eclipse is very nice and will highlight different bits of your code so that you can see the different bits of code more clearly. The code you write in Eclipse will tell your program what you want it to do when you run your code. With that explained, on with the programming!

1) Open up Eclipse It should look something like the screen shot below:

Eclipse interface

The green icon, which looks like the picture below, is used to run your programs. It can be found in the top bar and you have to click it to run the current program you are working in. Provided that your program has no errors, your program should run.

This appears in the top bar

Click on File->New->Java Project. Call the project name "cadmus" and click "Finish". Now right-click "cadmus" in the sidebar, then click New->Class and you should see the following pop-up: A new class

Where it says name type in Example then click Finish, and so your screen should look like this: And your new program begins

Notice the words public class in purple. A class is a file which contains objects and methods (which you will see in Chapter II). The word public just means that the piece of code can be used in other classes. The other word that we could have written in that space is private, so that only the class that we are currently in can use the piece of code.

At the top of a Java program, usually you can find a comment or two stating the name of the person who wrote the program and a note on what the program does. To write words and sentences in a program that other people can see when they look at your code, but isn't visible to the computer when you run your program, write // at the start of the sentence you want to write. So, I would write:

1// By Agent X; this is an example program.

This is to let other people who view my program know that the code was written by me, and likewise you would write your own name and the purpose of your program.

Now copy and paste this piece of code into your class:

1public static void main(String[] args) {
2
3}

This is the main method, and every Java program needs a main method. It is the first bit of code your program looks at when it is run. If you have more than one main method, your program will get confused and will not know what to do. (Where should it be starting from? This main method or that one?) So, the point is, you can only have ONE main method per program. You can run other methods from the main method too. The main method must always begin with that line and the file should look like the last screenshot. Bear in mind that you cannot change the name of the main method or not use one, and you must also keep the class name the same once you make the class (i.e. once you call your class 'Example' you cannot change that). By the end of your course, you will have seen the main method so many times you'll be able to memorise it.

Write your first computer program: Hello World →