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About the Java Technology
Java technology is both a high level 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:
- Object Oriented
- Architecture neutral
- High performance
- API based
- Open source
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 tool.
A .class file does not contain code that is native to your processor; it instead contains byte codes – the machine language of the Java Virtual Machine (JVM).
The java launcher tool then runs your application with instance of the Java Virtual Machine.
Because the JVM is available on many different Operating Systems, the same .class files are capable of running on Windows, Solaris, Linux or Mac OS. Some virtual machine, such as the Java SE HotSpot at a Glance, 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.
A platform is the hardware or software environment in which a program runs. We’ve already mentioned some of the most popular platforms like Microsoft Windows, Linux, Solaris OS, and Mac OS. Most platforms can be described as a combination of the operating system and underlying 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
- The Java Application Programming Interface (API)
You’ve already been introduced to the JVM; it’s the base for the Java platform and is ported onto various hardware-based platform.
The API is a large collection of ready-made software components that provide many useful capabilities. It is grouped into libraries of related classes and interfaces; these libraries are known as package. The next section, What Can Java Technology Do? Highlights some of the functionality provided by API.
The API and JVM insulate the program from the underlying hardware.
As a platform-independent environment, the Java platform can be a bit slower than native code. However, advance in compiler and virtual machine technologies are bringing performance close to that of native code without threatening portability.
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