Installing Java Development Kit

The Java Development Kit includes the essential development tools (JDK) and the Java Runtime Environment (JRE). The development tool compiles the Java source code into byte codes and the JRE is the response to execute the byte codes. We will need several Java compilations in later chapters. SmartFoxServer is build on the Java environment and we need the JRE to start up the server. The JDK and JRE may be pre-installed in some OSs.

Installing JDK On Windows

The steps for installing JDK on Windows are as follows:

1. Go to http://java.sun.com/javase/downloads/.
2. Click on the Download button of Java. It will lead to the Java SE Downloads page.
   
3. Select Windows (or Windows x64 for 64-bits Windows) in Platform.
4. Click on Download.
5. If it prompts an optional login request, we can click the Skip this Step to bypass it.
6. Launch the installer after the download.
7. Install the Java Development Kit with all default settings.
8. The Java environment is ready after installation completes.

Installing JDK on Mac OSX

The Mac OSX comes with its own set of Java environment. We can check the JDK and JRE version by following steps:

1. Launch terminal from Applications | Utilities | Terminal.
2. Type the following and press the Enter key:

   javac -version
   

3. The command will output the currently installed version of the Java in the Mac OSX. In my case, it outputs: javac 1.6.0_17.

The current version of SmartFoxServer at the time of writing recommends the version 1.6. If the Java is not updated, we can update it via Apple Menu | Software Update.

The software update will check for any updates for your existing Mac software, including the Java environment.

Installing JDK on Linux

We can use the general method to download and install the JDK or use the system specific method to install the package. We will show the general method and the Ubuntu method.

Installing for General Linux

1. Go to http://java.sun.com/javase/downloads/index.jsp in browser.
2. Click on the Download button.
3. The platform Linux should be selected automatically. Otherwise, select Linux (or Linux x64 for 64-bit Linux).
4. Click on Continue.
5. If it prompts for login, click on Skip this Step to bypass it.
6. For Redhat or Fedora Linux, choose the rpm-bin file to download. For other Linux, choose the .bin file to download.
7. Launch terminal via Applications | Accessories | Terminal after the download completes.
8. Change the directory to the folder that contains the downloaded package. The download destination varies from different profile settings. In my case, it is in Downloads folder.

   cd ~/Downloads/
   

9. The version is Java 6 Update 20 at the time of writing and the filename is jdk-6u20-linux-i586.bin or jdk-6u20-linux-i586-rpm.bin.
10. Then we make it executable and launch the installer by the following commands:

    chmod a+x jdk-6u20-linux-i586.bin ./jdk-6u20-linux-i586.bin
    

11. The installer displays the license agreement. Type Yes at the end to agree and continue installation.
12. Press the Enter key after the file's extraction to end the installation.
    

Installing for Ubuntu Linux

Ubuntu users can install the JDK via the apt-get command.

1. We will search for the latest package name of the JDK by the following command:

   apt-cache search --names-only sun-java.*-jdk
   

2. The result shows the available JDK packet names. At the time of writing, it is JDK6:

   sun-java6-jdk - Sun Java(TM) Development Kit (JDK) 6
   

3. We use the apt-get command to install the JDK:

   sudo apt-get install sun-java6-jdk
   

4. Type in the user password because it requires user's password and the privilege to use apt-get.