Java Virtual Machine
A Java Virtual Machine is quite simply a piece of software that enables Java technology to be recognized and successfully executed on a vast array of hardware platforms. Java virtual machines are so named because they provide a necessary environment for the Java bytecode to be executed. The flexibility of a JVM allows a Java applet to be written only once, but able to be run on virtually any operating system.
Java virtual machines accept standardized binary format code. Java compilers translate this code into the necessary format needed before it is run on a JVM. This organized approach ensures the portability and stability of Java to be implemented on such a wide array of hardware devices.
Java applets run in a user’s web browser and provide functionality that cannot be performed by HTML, such as games, calculators, and chat applications. In order to run a Java applet, a Java plug-in must be installed and the JVM must be running. Java applets are considered very safe to run, even if they are unknown or untested, since they are essentially isolated from the rest of the computer’s functionality. This isolation technique is often referred to as the sandbox.
There is no shortage of support for Java and Java virtual machines. Large corporations such as Apple, IBM, and Hewlett-Packard develop closed-source (proprietary, thus not made public) Java virtual machine implementations. There is also a large amount of interest and support from the open-source development community for developing Java virtual machines. Open source simply means that the source code is available to anyone for free to further develop and improve upon.
Though Java is typically enabled by default on popular browsers such as Internet Explorer, due to the malicious intent of hackers and unscrupulous web marketers, some web surfers feel safer by disabling Java. This can eliminate some of the very annoying pop-under advertisements that exploit the Java permissions that are typically left to default settings. Java can typically be accomplished in the browser’s preferences menu.
Sun distributes the JVM as part of the JRE and also as part of the J2EE, J2SE, and J2ME.
|
|
- Java Bytecode
Java bytecode is produced by the Java compiler and executed by the JVM (Java Virtual Machine). Java bytecode isn’t exactly source code, and it isn’t exactly compiled code, it’s something in the middle. Java bytecode is one of the things that make it possible for Java code to run on many different platforms. [...]...
- Java Source Code
Java source code is code that you write in the Java programming language. Java source code is converted to Java bytecode by the Java compiler. Java source code files usually have the .java extension. Sun recommends that Java source code files be no longer than two thousand lines. Larger source code files should be split [...]...
- Java vs. JavaScript
Java and JavaScript are two different programming languages which have similar names and share similar syntax. Java is a complete object oriented programming language which is designed to create applets or stand-alone applications. JavaScript is a more simple programming language which is designed to create scripts for use on the World Wide Web. Java bytecode [...]...
- Java Package
A Java package is a set of classes which are grouped together. This grouping helps to organize Java classes and codevent multiple Java classes with the same name. Using Java Packages To use a package in your Java source code, you must either import the package or use the fully qualified class name each time [...]...
- Java Class
A Java class is a group of Java methods and variables. Each Java source code file can contain one public class. The name of this public class must match the name of the Java source code file. If the public class is called “ballistics,” then the filename would be “ballistics.java.” Example Java Class class Ammunition [...]...