What is a Java Virtual Machine (JVM)?

To understand the Java virtual machine you must first be aware that you may be talking about any of three different things when you say "Java virtual machine." You may be speaking of:

• the abstract specification,
• a concrete implementation, or
• a runtime instance.

The abstract specification is a concept, described in detail in the book: The Java Virtual Machine Specification, by Tim Lindholm and Frank Yellin. Concrete implementations, which exist on many platforms and come from many vendors, are either all software or a combination of hardware and software. A runtime instance hosts a single running Java application. Each Java application runs inside a runtime instance of some concrete implementation of the abstract specification of the Java virtual machine. In this book, the term "Java virtual machine" is used in all three of these senses. Where the intended sense is not clear from the context, one of the terms "specification," "implementation," or "instance" is added to the term "Java virtual machine".

Creating a JAR File using Eclipse IDE

JAR file using Eclipse IDE

Creating JAR file using Eclipse IDE is pretty much easy. Follow the simple steps.
Right click on your project, which you want to create a JAR file of. And select Export from the context menu.

Select JAR file from Java folder and click Next.

Provide the Destination path and click on Finish to create the JAR.