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Java Programming
Java was developed by Sun Microsystems, Inc. as an Object-oriented
programming language that can run on many different computer
platforms.
This technology provides a degree of interactivity
and customization that is unprecedented in previous business
communications. Many say that Java will change the face of computer
programming as we know it.
Java programs that run inside a Web
browser are called Java Applets. Java Applets are the most common
use of the Java language on the Web. However, Java is powerful
enough for stand-alone applications also.
Learn More About Java
The Java™ programming language is robust and versatile, enabling developers to:
- Write software on one platform and run it on another.
- Create programs to run within a web browser.
- Develop server-side applications for online forums, stores, polls, processing HTML forms, and more.
- Write applications for cell phones, two-way pagers, and other consumer devices.
It's no wonder the Java platform attracts so many new developers.
About the Java Technology
Java technology is both a programming language and a platform.
The Java Programming Language
The Java programming language is a high-level language that can be characterized by all of the following buzzwords:
- Simple
- Architecture neutral
- Object oriented
- Portable
- Distributed
- High performance
- Interpreted
- Multi-threaded
- Robust
- Dynamic
- Secure
With most programming languages, you either compile or interpret a program so that you can run it on your computer. The Java programming language is unusual in that a program is both compiled and interpreted. With the compiler, first you translate a program into an intermediate language called Java byte codes -the platform-independent codes interpreted by the interpreter on the Java platform. The interpreter parses and runs each Java byte code instruction on the computer. Compilation happens just once; interpretation occurs each time the program is executed.
You can think of Java byte codes as the machine code instructions for the Java Virtual Machine (Java VM). Every Java interpreter, whether it's a development tool or a Web browser that can run applets, is an implementation of the Java VM.
Java byte codes help make "write once, run anywhere" possible. You can compile your program into byte codes on any platform that has a Java compiler. The byte codes can then be run on any implementation of the Java VM. That means that as long as a computer has a Java VM, the same program written in the Java programming language can run on Windows 2000, a Solaris workstation, or on an iMac.
The Java Platform
A platform is the hardware or software environment in which a program runs. We've already mentioned some of the most popular platforms like Windows 2000, Linux, Solaris, and MacOS. Most platforms can be described as a combination of the operating system and hardware. The Java platform differs from most other platforms in that it's a software-only platform that runs on top of other hardware-based platforms.
The Java platform has two components:
- The Java Virtual Machine (Java VM)
- The Java Application Programming Interface (Java API)
You've already been introduced to the Java VM. It's the base for the Java platform and is ported onto various hardware-based platforms.
The Java API is a large collection of ready-made software components that provide many useful capabilities, such as graphical user interface (GUI) widgets. The Java API is grouped into libraries of related classes and interfaces; these libraries are known as packages.
Native code is code that after you compile it, the compiled code runs on a specific hardware platform. As a platform-independent environment, the Java platform can be a bit slower than native code. However, smart compilers, well-tuned interpreters, and just-in-time byte code compilers can bring performance close to that of native code without threatening portability.
What is JavaTM Technology?
You're here because you've probably heard of the word "Java" in some form and want to know more.
Let's start with the big picture:
The Java™ platform is based on the power of networks and the idea that the same software should run on many different kinds of computers, consumer gadgets, and other devices. Since its initial commercial release in 1995, Java technology has grown in popularity and usage because of its true portability. The Java platform allows you to run the same Java application on lots of different kinds of computers.
Any Java application can easily be delivered over the Internet, or any network, without operating system or hardware platform compatibility issues. For example, you could run a Java technology based application on a PC, a Macintosh computer, a network computer, or even new technologies like Internet screen phones. Furthermore, the Java platform was designed to run programs securely on networks, which means that it integrates safely with the existing systems on your network.
The idea is simple: Java technology-based software can work just about everywhere. Java technology components don't care what kind of computer, phone, TV, or operating system they run on. They just work, on any kind of compatible device that supports the Java platform.
Java technology allows programmers and users to do new things with Web pages that were not possible before. With Java technology, the Internet and private networks becomes your computing environment. For example, users can securely access their personal information and applications when they're far away from the office by using any computer that's connected to the Internet; soon they'll be able to access tailored applications from a mobile phone based on the Java platform, or even use smart cards as a pass key to everything from the cash machine to ski lifts.
Smart Card or Smart Java Card™
A smart card is a credit card-sized plastic card with an integrated circuit (IC) inside. The IC contains a microprocessor and memory, which gives smart cards the ability to process, as well as store, more information than was previously possible.
In the case of the Java Card platform, applications in the form of byte-code are loaded into the memory zone of the smart card's microprocessor, where they are run by the Virtual Machine. The executable code is platform independent so that any card incorporating a Java Card technology-based interpreter can run the same application.
Multiple Java Card technology-based applications can reside on a single card, each allocated to their own secure memory areas to ensure their integrity and eliminate program tampering, either by individuals or through program interference.
The Java platform is being built into next-generation telephones, TV set-top boxes, smart cards that fit in your wallet, and many other consumer and business devices. Java technology-based software includes: programs written in the Java programming language can run directly on your computer (without requiring a browser), or on servers, on large mainframe computers, or other devices.
For example, Java technology-based software running on servers in large companies monitors transactions and ties together data from existing computer systems. Other companies are using Java technology-based software on their internal Web sites to streamline communication and the flow of information between departments, suppliers and customers.
Programs written in the Java programming language run on so many different kinds of systems thanks to a component of the platform called the Java virtual machine or "JVMTM"* -- a kind of translator that turns general Java platform instructions into tailored commands that make the devices do their work.
If you're reading this in a Web browser on a personal computer or workstation, you've probably already got the Java platform. It's incorporated into all major Web browsers. In the event that a JVM is not incorporated, Sun provides a fully supported, high-performance virtual machine as part of the Java 2 Runtime Environment, Standard Edition (JRE), available for download from the J2SETM platform homepage.
You don't need to be a mechanic to drive a car. Why should you have to be a "system administrator" to use a computer? With Java software, you don't have to be one. Java technology eliminates many of the problems associated with installing and running applications. That's because generally the Java user does not have to configure, load, or install anything. Instead, computing devices tap into the network and funnel its power to the user. Upgrades are automatic, making installation and configuration obsolete.
Ease of Development: Two Real-Life Example. Developing on the Java platform means that projects are completed faster and with less debugging.
Having completed sizable development projects over the last three years, using different technologies, MVI Solutions has come to endorse only the Java 2 Platform, Enterprise Edition for enterprise Web application development.
Leveraging the J2EETM [platform's] suite of technologies enabled us to focus more of our technical resources on creating solutions to business problems, rather than laboring to maintain proprietary software from Microsoft. In addition, Java technology's underlying object oriented architecture allowed us to design our systems for maximum code reuse. We have also taken advantage of Java technology's portability by running our production application on both Windows NT and Solaris™ 8.0 Operating Environment with no code changes.
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