Java for Linux: Blackdown

To develop Java applications, use Java tools, and run many Java products, you must install the Java 2 Software Development Kit (SDK) and the Java 2 Runtime Environment (JRE) on your system. Together, they make up the Java 2 Platform, Standard Edition (J2SE). Sun currently supports and distributes Linux versions of these products. You can download them from Sun at java.sun.com/j2se and install them on your system. You can even select an RPM package version for easy installation on Red Hat. The current version of the J2SE is known as Java version 1.4. An earlier version, 1.2, will not work on Red Hat 7.0, though 1.3 will work on 7.1 and up.

Though Sun supports Linux versions of Java, more thorough and effective Linux ports of Java can be obtained from the Blackdown project at www.blackdown.org. The Blackdown project has ported the J2SE, including versions 1.4 of the SDK and JRE . They have also ported previous versions of Java, including 1.1, 1.2, and 1.3. More information and documentation is also available at this Blackdown Web site. The SDK and JRE 1.4 are usually available in the form of compressed archives, .tar.bz2. You use the bunzip2 command to decompress the file and the tar xvf command to extract it. Extraction should be done in the /usr/local file. Follow the instructions in the INSTALL file to install the software.

Numerous additional Java-based products and tools are currently adaptable for Linux. Tools include Java 3D, Java Media Framework (JMF), and Java Advanced Imaging (JAI), all Blackdown projects (see Table 14-3). Many of the products run directly as provided by Sun. These include the HotJava Web browser and the Java Web server. You can download several directly from the Sun Java Web site at java.sun.com.

Table 14-3: Blackdown Java Packages and Java Web Applications
Application	Description
Java 2 Software Development Kit (SDK) 1.4	A Java development environment with a compiler, interpreters, debugger, and more. Part of the Java 2 Platform. Download the Linux port from www.blackdown.org.
Java 2 Runtime Environment 1.4 (J2RE)	A Java Runtime Environment used to run Java applets. Part of the Java 2 Platform. Download the Linux port from www.blackdown.org.
Java 2 Platform SE (J2SE) for Linux 1.4	Java 2 Platform, Standard Edition, which includes Java 2 SDK and RE. Download the Linux port from www.blackdown.org.
Java 3D for Linux	Sun's 3D Application Program Interface for 3D Java programs. Download the Linux port from www.blackdown.org.
Java Media Framework (JMF) for Linux	Enable audio and video to be added to Java. Download the Linux port from www.blackdown.org.
Java Advanced Imaging (JAI) for Linux	Java Advanced Imaging API. Download the Linux port from www.blackdown.org.
Java 1.1 Development Kit (JDK) and Java 1.1 Runtime Environment (JRE)	The older Java 1.1 development environment with a compiler, interpreters, debugger, and more. Download the Linux port for your distribution's update through www.blackdown.org.
HotJava browser	Sun's HTML 3.2– and JDK 1.1–compliant Web browser. Download the Linux version from java.sun.com.
Java Web Server	A Web server implemented with Java. Available at Java Web site at java.sun.com.
GNU Java Compiler	GNU Public Licensed Java Compiler (GJC) to compile Java programs, gcc.gnu.org/java.

Note

See java.sun.com/products for an extensive listing of Java applications.

The Java 2 Software Development Kit: SDK

The Java Software Development Kit (SDK) provides tools for creating and debugging your own Java applets and provides support for Java applications, such as the HotJava browser. The kit includes demonstration applets with source code. You can obtain detailed documentation about the SDK from the Sun Web site at java.sun.com. Three major releases of the SDK are currently available—1.2, 1,3, 1.4.x—with corresponding versions for the Java 2 Runtime Environment (J2RE) for 1.2, 1.3, and 1.4. The Java SDK adds capabilities for security, GUI support with JFC (also know as Swing), and running Java enhancements, such as Java 3D and Java Sound.

The SDK includes standard features found in the JDK features for internationalization, signed applets, JAR file format, AWT (window toolkit) enhancements, JavaBeans component model, networking enhancements, a math package for large numbers, database connectivity (JDBC), object serialization, and inner classes. Java applications include a Java compiler (javac), a Java debugger (jdb), and an applet viewer (appletviewer). In addition, the SDK offers the Java Naming and Directory Interface (JNDI), integrated Swing, Java 2D, network and security enhancements, and CORBA. With SDK, you can run the Blackdown port of Java 3D, Java Advanced Imaging, Java Media Framework, and Java Sound. Detailed descriptions of these features can be found in the SDK documentation.

You create a Java applet much as you would create a program using a standard programming language. You first use a text editor to create the source code, which is saved in a file with a .java extension. Then you can use the javac compiler to compile the source code file, generating a Java applet. Numerous integrated development environment (IDE) applications are available for composing Java applets and applications. Although most are commercial, some provide free shareware versions. An IDE provides a GUI interface for constructing Java applets. You can link to and download several IDE applications through the Blackdown Web page.