About the Java Technology
The JavaTM programming language is designed to meet the challenges of application development in the context of heterogeneous, network-wide distributed environments. Paramount among these challenges is secure delivery of applications that consume the minimum of system resources, can run on any hardware and software platform, and can be extended dynamically.
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
Multithreaded
Robust
Dynamic
Secure
Ø Your programming language is object oriented, yet it's still dead simple.
Ø Your development cycle is much faster because Java technology is interpreted. The compile-link-load-test-crash-debug cycle is obsolete--now you just compile and run.
Ø Your applications are portable across multiple platforms. Write your applications once, and you never need to port them--they will run without modification on multiple operating systems and hardware architectures.
Ø Your applications are robust because the Java runtime environment manages memory for you.
Ø Your interactive graphical applications have high performance because multiple concurrent threads of activity in your application are supported by the multithreading built into the Java programming language and runtime platform.
Ø Your applications are adaptable to changing environments because you can dynamically download code modules from anywhere on the network.
Ø Your end users can trust that your applications are secure, even though they're downloading code from all over the Internet; the Java runtime environment has built-in protection against viruses and tampering.
In the Java programming language, all source code is first written in plain text files ending with the .java extension. Those source files are then compiled into .class files by the javac compiler. A .class file does not contain code that is native to your processor; it instead contains bytecodes — the machine language of the Java Virtual Machine1 (Java VM). The java launcher tool then runs your application with an instance of the Java Virtual Machine.
Figure A. An overview of the software development process.
Because the Java VM is available on many different operating systems, the same .class files are capable of running on Microsoft Windows, the Solaris TM Operating System (Solaris OS), Linux, or Mac OS. Some virtual machines, such as the Java HotSpot virtual machine, perform additional steps at runtime to give your application a performance boost. This include various tasks such as finding performance bottlenecks and recompiling (to native code) frequently used sections of code.
Through the Java VM, the same application is capable of running on multiple platforms.
The Java Platform
