You will need to download and install the free Java JDK from the Oracle/Sun website. As of November, 2012, you will find that website at http://www.oracle.com/technetwork/java/javase/downloads/index.html

There is a 64-bit version of the JDK, but I haven't tried it yet because my home computer won't can't support it. I am still using the 32-bit version. However, I suspect that the 64-bit version will work just fine if you have a computer that supports it.

Whether you elect to use the 32-bit or 64-bit version is strictly up to you. Either of them should do the job very nicely.

As of November 2012, you will find installation instructions at http://download.oracle.com/javase/7/docs/webnotes/install/windows/jdk-installation-windows.html .

I strongly recommend that you read the instructions and pay particular attention to the information 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

... ;C:\Program Files (x86)\Java\jdk1.6.0_26\bin

in place of

... ;C:\Program Files\Java\jdk1.7.0\bin

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.

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 http://www.oracle.com/technetwork/java/javase/documentation/index.html .

Specific documentation for classes, methods, etc., is available online at http://download.oracle.com/javase/7/docs/api/ .

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 documentation are also shown on the page at http://www.oracle.com/technetwork/java/javase/downloads/index.html .

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 the name 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) .

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.

echo off
cls

del *.class

javac -cp .; hello.java
java -cp .; hello

pause

Comments regarding the batch file

The commands in the batch file of Listing 1 will

If errors occur, they will be reported on the command-line screen and the program won't be executed.

If your program is named something other than hello , (which it typically would be) substitute the new name for the word hello where it appears twice in the batch file.

Don't delete the pause command

The pause command causes the command-line window to stay on the screen until you dismiss it by pressing a key on the keyboard. You will need to examine the contents of the window if there are errors when you attempt to compile and run your program, so don't delete the pause command.

Translate to other operating systems

The format of the batch file in Listing 1 is a Windows format. If you are using a different operating system, you will need to translate the information in Listing 1 into the correct format for your operating system.

The test program in Listing 2 can be used to confirm that Java is properly installed on your computer and that you can successfully compile and execute Java programs.

class hello {
  public static void main(String[] args){
    System.out.println("Hello World");
  }//end main
}//end class

Instructions

Copy the code shown in Listing 2 into a text file named hello.java and store in an empty folder somewhere on your disk.

Create a batch file named hello.bat containing the text shown in Listing 1 and store that file in the same folder as the file named hello.java .

Execute the batch file.

If everything is working, a command-line screen should open and display the following text:

Hello World
Press any key to continue . . .

Congratulations

If that happens, you have just written, compiled and executed your first Java program.

Oops

If that doesn't happen, you need to go back to the installation instructions and see if you can determine why the JDK isn't properly installed.

If you get an error message similar to the following, that probably means that you didn't set the path environment variable correctly.

'javac' is not recognized as an internal or external command,
operable program or batch file.

Beyond that, I can't provide much advice in the way of troubleshooting hints.