Manifest . A manifest is a list of passengers or an invoice of cargo for a ship. The meaning has
been generalized to a description of the contents of something, e.g. a jar file.
If you are using an IDE and you have told it which class has method main ,
any time you run the program, execution starts by calling method main .
Executing a Java program from the command line
In a DOS window or a command-line window, navigate to a directory that
contains a file Name.java (say) that:
1. Has a static procedure main with one argument that is a String array.
2. Has been been compiled, so that there is a file Name.class .
Then, the following command executes a call to method main of class java.
Name . The command should not include the suffix .class or .java .
A Java application may consist of many classes. If you want to give someone an
application, you have to give them all the .class files. That can be messy. Better
is to put the application in a single file that can be executed easily, perhaps by
double-clicking on its icon. You do this by making a jar file of the classes. Jar
stands for Java ARchive —after tar files (TapeARchives) on Unix systems.
To make a jar file with name app.jar , open a DOS or command-line win-
dow and navigate to the directory where the .java and .class files are. Type in
the following command (note: if command jar is not available, you will have to
change your path . See the end of this Sec. 16.2):
jar -cf app.jar *.class
The “c” in -cf is for create . The “f” is for file, and it indicates that the name
of the file to create follows, in this case, app.jar . The “ *.class ” is expanded
to name all the .class files in the directory. So, this command makes up a jar
file named app.jar , which contains all the .class files in the directory.
You still have to insert into the jar file something that tells it which class has
method main . Suppose it is class CMain . Then do the following:
(a) Make up a file x.mf that contains one line of text:
The suffix on x.mf stands for manifest . Make sure you hit the enter key after typ-
ing the text in the file because it must have a carriage-return or line-feed in it.
You can create file x.mf in wordpad, notepad, DrJava, or any editor you want.
Make sure the file is in the same directory as file app.jar .