A jar file allows you to bundle a group of java
classes (e.g., a project in BlueJ or JCreator, for example)
into a single archive. In most operating systems,
java program execution simply involves double-clicking
the jar file.
Here are the steps needed to build a jar file
(try it on one of our JFrame examples):
Make sure all java programs required for
execution of the project are compiled in one folder.
In that same folder, create a text file (e.g., main.txt),
containing a single line:
Main-class: MainProgram
where MainProgram is the java class that contains the
main method. (Important: there should be exactly one space
after the colon.)
Execute a command prompt, cd to
the folder containing the .class files and main.txt, and
type:
jar cmvf main.txt PROG.jar *.class
A PROG.jar file will be created. Move that file
anywhere in your system, double-click, and watch your
program execute.