2.2 Jb0110: java oop: programming fundamentals, getting started  (Page 2/3)

Installing the JDK

As of November 2012, you will find installation instructions at (External Link) .

I strongly recommend that you read the instructions and pay particular attention to theinformation having to do with setting the path environment variable.

A word of caution

If you happen to be running Windows Vista or Windows 7, you may need to use something like the following when updating the PATH Environment Variable

in place of

as shown in the installation instructions.

I don't have any experience with any Linux version. Therefore, I don't have any hints to offer there.

The JDK documentation

It is very difficult to program in Java without access to the documentation for the JDK.

Several different types of Java documentation are available online at (External Link) .

Specific documentation for classes, methods, etc., is available online at (External Link) .

It is also possible to download the documentation and install it locally if you have room on your disk. The download links for JDK 6 and JDK 7 documentationare also shown on the page at (External Link) .

You may also want to search for and use the documentation for the latest version of the JDK.

Compiling and running Java code

There are a variety of ways to compile and run Java code. The way that I will describe here is the most basic and, in my opinion, the most reliable. These instructionsapply to a Windows operating system. If you are using a different operating system, you will need to translate the instructions to your operating system.

Write your Java program

Begin by using your text editor to write your Java program into one or more text files, each with an extension of.java. (Files of this type are often referred to as source code files.) Save the source code files in an empty folder somewhere on your disk. Make sure that thename of the class containing the main method (which you will learn about in a future module) matches the name of the file in which that class is contained (except for the extension of .java on the file name, which does not appear in the class name) .

Create a batch file

Use your text editor to create a batch file (or whatever the equivalent is for your operating system) containing the text shown in Listing 1 (with the modifications discussed below) and store it in the same folder as your Java source code files..

Then execute the batch file, which in turn will execute the program if there are no compilation errors.

Comments regarding the batch file

The commands in the batch file of Listing 1 will

• Open a command-line screen for the folder containing the batch file.
• Delete all of the compiled class files from the folder. (If the folder doesn't contain any class files, this will be indicated on the command-linescreen.)
• Attempt to compile the program in the file named hello.java.
• Attempt to run the compiled program using a compiled Java file named hello.class .
• Pause and wait for you to dismiss the command-line screen by pressing a key on the keyboard.