JAVA , Yet Another Language ?

Java computing is a worldwide phenomenon, a language for network programming that was developed by Sun Microsystems under the guidance of James Gosling and Bill Joy. It is already in widespread use for creating fun and interesting animated Web pages. Java language and environment are rich enough to support entirely new kinds of applications, like dynamically extensible browsers. It is designed to be a machine independent programming language that is both safe enough to traverse networks and powerful enough to replace native executable code. The increasing importance of networks is placing new demands on existing tools, and fueling the demand for a rapidly growing list of completely new kinds of application.

With Java, we can have a fast, portable and secure software that works on any platform and plays with any applications; dynamic applications that take advantage of a connected world, capable of accessing disparate and distributed information sources; a truly distributed software that can be extended and upgraded; an intelligent applications that can roam the Net for us, ferreting out information and serving as electronic emissaries.

Sun Microsystems patriarch, James Gosling, is the one who will be remembered as the father of Java. In the eighties, Gosling had designed the Sun's NeWS window system, which briefly contended with the X Window System for control of the UNIX graphic user interface desktop (GUI). However, NeWS was lost out to X, because Sun kept it proprietary and didn't publish the source code.

In the failure of NeWS, Gosling has learnt that the power of integrating expressive language with a network-aware windowing GUI, and the Internet programming community will refuse to accept proprietary standards, no matter how good they may be.

In 1992, the Sun subsidiary, FirstPerson team worked on developing software for information appliances. The goal was to enable the transfer of information and real-time applications over cheap infrared and packet-based networks. Memory and bandwidth limitations dictated small and efficient code. The nature of the applications also demanded they to be safe and robust. Gosling and his teammates began programming in C++, but they soon found that it is too complex, unwieldy and insecure for the task, so they start from scratch again !

Then, Sun shifted FirstPerson's efforts to interactive TV (ITV), and the programming language for the ITV set-top boxes was Oak. Oak is elegance and able to provide safe interactivity, but it could not reduce the lost cause of ITV.

In 1993, the explosion of interest in Internet, and the World Wide Web (WWW) presented a new opportunity. Oak was small, robust, architecture independent, and object oriented. These are just the requirements for a universal, network programming language. Sun quickly changed focus, and with a little retooling, Oak became Java.

Java is a curious mixture of C++ and Smalltalk. It has the syntax of C++, making it easy to learn. It has improved on C++ in some of the important areas, because C++ proved to be inadequated for certain tasks, those language features which make C++ unsafe and hard to read are removed to make Java, which include #define, typedef, multiple inheritance, operator overloading, enum, unions, structs, pointer arithmetic, global variables, standalone functions, friend functions and non-virtual functions. Like Smalltalk, Java has garbage collection, a feature that frees the programmer from explicitly allocating and de-allocating memory, It runs on a Smalltalk-style virtual machine, software built into your web browser which executes the same standard compiled Java bytecodes no matter what type of computer you have .

In Java, the basic builing blocks are the Java Applet and Application. Java also has a number of features that make it safer, these include true arrays with bounds checking, garbage collection, councrrency, interfaces and packages. There is no need to explicitly allocate or free memory in Java.

• Garbage collection - It is used to remove objects that are no longer needed. The garbage collector is usually a low priority thread; it counts references to the objects periodically, when all references to an object are gone, it is no longer accessible, the garbage collection mechanism reclaims it and returns the space to the available pool of resources.

• Reference - Java does not use pointers, instead it uses references, which is an abstract identifier for an object. A reference tags a particular object with a name in the Java virtual machine (JVM), so that the programmer may refer to it. The exact way of how the JVM implements references at the level of machine code is completely hidden from the programmer. Also it is VM dependent, so other schemes are possible, while Sun's VM uses handles and Microsoft's does use pointers.

• Interface - Java doesn't support multiple inheritance. Therefore interfaces are used instead, which are unique to the language, and played a role similar to that of multiple inheritance in other object-oriented languages. An interface is essentially a special kind of class, contain methods and variables, but completely abstract. Declare interfaces for each additional class you want to inherit from, and implement those interfaces in your subclass.

• Multi thread - It is similar to multi-processing, with multi-threading all execution contexts share the same memory, this makes sharing data between threads simpler than sharing data between processes. Thread provide synchronous execution. The advantages of using multi-threading is the apparent in graphical user interfaces and in applets, severs and simulations.

• Packages - It is used for managing namespaces; it can thought of as a container for related classes and interfaces, and the Java standard library was divided into packages.

• Exception handling - It used as error management; an exception, likes an interrupt during the execution of a program. Java uses exceptions to provide error handling capabilities for its programs. When an error occurs with a Java method, it creates an exception object and hands it to the run-time system.

Finally Java was designed to make it a lot easier to write bugfree code. Shipping C code has, on average , one bug per 55 lines of code. About half of these bugs are related to memory allocation and deallocation. Thus Java has a number of features to make bugs less common.

1. strong typing
2. no unsafe constructs
3. the language is small ,easy to become fluent
4. the language is easy to read and write
5. no undefined or architecture dependent constructs

• Portable - Java was designed to be cross-platform in source form, also in compiled binary form. Since this is impossible across processor architectures, Java is compiled to an intermediate bytecode which is interpreted by the Java interpreter. Thus, to port Java programs to a new platform all that is needed is a port of the interpreter and a few native code libraries. So the Java program can run on any machine that has the Java interpreter, because of this feature, Java is used on network computing.

• Robust - The Java code is well behaved, and the need for solid applications that will not bring down a system when a user stumbles across a home page with a small animation.

• Secure and reliable - Java uses both compile-time and run-time checking to ensure reliablity. The Java environment protects the client against both intentional and unintentional attacks; also against any viruses and worms when the applications are download and run. Also, by removing the pointers from the memory management model, many common program errors are eliminated. Java programs cannot access arbitrary addresses in memory.

• Object-oriented - It allows inheritance and reuse of code both in static and dynamic fashion.

• High performance - It supports several high performance features such as multi-threading, just-in-time compiling, and native code usage.

• Easy - It is similar to C and C++, and is one of the easiest language to write.

Virtual Machine

Java Virtual Machine (JVM) is an abstract computer that runs compiled Java programs. It generally implemented in software on top of a "real" hardware platform and operating system. All Java programs are compiled for the JVM, and the compiled Java program will run on the platform which was implemented by the JVM. JVM is small when implemented in software, therefore, it can fit in as many places as possible, places like TV sets, cell phones, and personal computers.

JVM provides a layer of abstraction between the compiled Java program and the underlying hardware platform and operating system, so the compiled Java programs run on the JVM, which is independent of whatever may be underneath a particular JVM implementation. Therefore, programs written in Java will run everywhere.

Java program are compiled from the java source into a form called Java bytecode, also called J-code. The compiled bytecode is executed by a Java run-time interpreter, so it is like a machine language of the JVM. The run-time system performs all the normal activities of a real processor, but is does so in a safe, virtual environment.

The Java compiler reads Java language source (.java) files, translates the source into Java bytecodes, and places the bytecodes into class (.class) files.

To the JVM, a stream of bytecodes is a sequence of instructions. Each instruction consists of opcode and operand. The opcode tells the JVM what action to take. If the JVM requires more information to perform the action than just the opcode, the required information immediately follows the opcode as operands.

All of this has proved that Java code is implicitly portable. The same Java application can run on any platform that provides a Java run-time environment. You don't have to produce alternate versions of your application for different platforms, and you never have to distribute source code to end users.

Java is the latest, flashiest object-oriented language. It has taken the software world by storm due to its close ties with the Internet and Web browsers. It is designed as a portable, safe network programming language that can run on any web-enabled computer via that computer's Web browser. As such, it offers great promise as the standard Internet and Intranet programming language.

The development of the WWW started later than Java, but the advantage of Java to the web is that it provides a secure, cross-platform way for code to be executed. Java also provides several features to existing web sites to simplify the editing, like graphics and data type; it also improved on the loading to the server and make more user interaction.

Is there any alternatives ?

Microsoft's ActiveX, since Microsoft operating systems and applications are used in most desktop computers and a large percentage of servers, however, it is not a cross-platform solution, so applications developed using ActiveX eliminate all non Microsoft users from the consumer base.

Sun's JavaBeans component APIs for Java, represents a complete multi-platform solution. By developing to JavaBeans specifications, your code runs on every operating system and also within any application environment. JavaBeans actually provides interoperability with ActiveX, OpenDoc, and LiveConnect.

Sun's JavaScript is a compact, object-based scripting programming language for developing clinent and server Internet application. It is quite different from Java.

Just as Sun said "Write Once, Run Anywhere." is the ideal task for the Java platform, it saves developers time, saves their companies the expense of multiple ports and traditional distribution methods. The Java Platform bridges many varieties of hardware and system software with a common language.

Different platform will have a different architecture, for example, UNIX, Window and Macintosh are all different platform. Therefore, if we write a program in one of the platform, it may have problems if it runs on the other.

From platform to platform, we may have different conventions for line termination in a text file, different size of fonts, different size of screen, different number of colour available, this can lead to a illegal display or operation. Therefore, it is important to have a common language that can run on all platforms.

The number of Java platform is ever increasing; with the rapid expansion of the network computing, it is essential to have a portable network programming language and cross-platform. A cross platform architecture, need portability, produce the same result on any platform, fulfill its function on any platform, therefore portability is dependent on the functionality of a particular program.

Java development tools are being rapidly deployed, and are available from such major software companies as IBM, Microsoft; and Sun has made a Java development kit available for Sparc and X86 Solaris, Windows NT for Intel, Windows 95, MacOS 7.5 on PowerMacs and 68030 (25 MHz and faster) and 68040 Macx.

"We have a solid asset in this thing called Windows, so how do we invest and further that platform and still respond to the cross-platform needs that make Java and the network computer so popular? That is what we have to figure out." said one source at Microsoft. And Microsoft is rewriting a key windows technology, its Distributed COM (Component Object Model) transport, in Java, to extend its reach to make it multiplatform.

We can see the importance of making the language portable to allow cross-platform application.

Java has been adopted faster than any other software technology, most developers are now written in Java, and most companies are using Java applications to create competitive advantages, increase revenues, and cut costs. Java computing model helps businesses solve some of the most pressing challenges they currently face: building corporate intranets, complexity of the computing environment, high administration and support costs, product incompatibilities, long product development cycles, and end-user frustration. It enables business to complement their traditional architectures with new Java capabilities.

In 1996, Sun introduced Java Enterprise Computing, it is an end-to-end, secure network computing solution based on distributed Java applications and low-cost Java network devices. Recently, Sun has announced that the formation of the Java Financial Objects XChange (JFOX), an organization of top financial houses and computer companies aimed at promoting the use of Java applications in financial transactions and banking. JavaBeans component architecture may be used as the foundation for major financial transaction applications for functions such as trading, consumer banking, risk management and insurance-claims processing.

Java is a easy to use, fast, portable and secure programming language, which is most suitable for networking computing, it is not only used for creating animated web pages, but also helping the real world business to make money.

1. PowerPC Microprocessor Common Hardware Reference Platform
    by Morgan Kaufmann

2. Towards A Java Compiler
    by Ying Xiong

3. Exploring Java
    by Niemeyer & Peck

4. JavaSoft Home Page

5. Gamelan

6. Club Java: sponsored by Virutal Rendezvous

7. What is Object-Oriented Software ?

8. Java World - IDG's magazine for the Java Community

9. JavaScript Authoring Guide