Inline::java STUDY configuration - perl

Question

The Inline docs aren't too helpful in learning how to use the STUDY config,
can anyone clarify the syntax involved in calling a simple void method that prints a method, say, Hello() ?
Also, in terms of the external java file, is there a specific directory i need to put it in, or does it go in the same directory of the perl script?

Answer 1

Let's start with the file /home/foo/java_src/Hello.java, which contains:
public class Hello {
public Hello() {}
public void instance_hello() { System.out.println("hello world"); }
public static void static_hello() { System.out.println("HELLO WORLD"); }
}
Tackling your second question first, the first argument after use Inline Java ... can be a filename, and so you can put your source file anywhere and refer to it by its file name in your perl code:
use Inline Java => '/home/foo/java_src/Hello.java';
$obj = Hello->new();
$obj->instance_hello(); # "hello world"
Hello->static_hello(); # "HELLO WORLD"
Note that you don't need STUDY so far. The Hello class is defined in source code that is read directly by the Inline::Java module, so the module automatically creates and populates the Hello namespace in Perl.
STUDY is for classes that aren't parsed directly by Inline::Java. So let's say instead that our Hello class has been compiled into a jar file called /home/foo/jars/hello.jar. Now to use the Hello class you would need to (1) include hello.jar in your CLASSPATH and (2) use STUDY to tell Inline::Java to create the Hello namespace:
use Inline Java => 'STUDY',
CLASSPATH => '/home/foo/jars/hello.jar',
STUDY => ['Hello'];
$obj = Hello->new;
Hello->static_hello; # "HELLO WORLD"
$obj->instance_hello; # "hello world"
We include the first argument STUDY to signal to the Inline::Java that we're not passing any source code directly to the module. We could have also passed valid source code or a valid source code filename.
use Inline Java => 'public class Nothing() { }',
CLASSPATH => '/home/foo/jars/hello.jar',
STUDY => ['Hello'];