Java on the Command Line
You can run Java programs from the command line through the java command. Generally, you invoke it in one of two ways:
-
java
options
class
argument1 argument2...
Loads the specified class and runs its main method. If it has no such method, or if it’s of the wrong format,[13] then the class will fail to launch.
You should have a class path defined so that the Java interpreter will know where on the filesystem to search for the specified class. See Section 10.4.1.
-
java
options
-jar
jarfile
arguments
In this case, the -jar option tells the Java interpreter to launch a program encapsulated in a Jar (Java Archive) file.[14] This works only if the Jar file knows its own Main-class, which defines the main method.
Jar files, like Mac OS X applications, are self-contained and ignore the user’s class path definitions.
Tip
This section involves using the Terminal. If you are completely unfamiliar with this application, or with using a Unix command line in general, you may want to skip ahead to Chapter 19 first.
You can find a full list of Java’s options under its manpage, but here are some of the more useful ones:
-
-cp
Lets you define the class path for one command invocation. See Section 10.4.1.
-
-D
property=value
Sets a system property value.
-
-verbose
Displays information about each loaded class.
Tip
If the Java program you wish to run from the command line happens to be a self-contained Mac OS X application (of the sort described earlier in Section 10.2), then ...
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