Properties Class, How does it work

Question

Hi
I was struggling to find how to use Properties Object, to read properties file, then I saw the following solution:
fis = <classname>.getClass().getResourceAsStream("<prop file>"); (1)
prop = new Properties();(2)
prop.load(fis);(3)
fis.close();(4)
This works fine, but I am not able to understand, how does it work?
<classname>.getClass() should return a class object, and this class must be havaing getResourceAsStream() method, which is used by the properties object. But what is the need of first getting a "class" object. Our aim is to open the Properties file, then why do we need any reference to the current class.
Can anybody explain the jargon of the line -(1)
Gaurav

Answer 1

the Class class is defined in the lava.lang package. The java virtual machine (JVM) uses a class loader to load class definitions from wherever <g> into memory, ok? The Class class represents the JVM's internal holding of a class definition (as opposed to instances of the class itself).
To get the Class for any class, you can use the getClass() method on any object, or you can use the <classname>.class syntax. Either way, you get an instance of Class.
The Class class contains some utility methods about class definitions prresent in the JVM. Importantly, the Class object for a class contains a reference to the class loader that loaded the class. You get it with the getClassLoader() method. The class loader is a thing that knows how to get a class definition from a local drive, or of a jar file, or off the web (if you are using an applet), or whatever. If one class needs another class to work, the class loader knows how to get the definition for that other class.
Say I have a class
class Foo {
   int bar(Baz baz);
}and another one
class Baz {
}And both of these are in a jar file at http://z.com/applet1.jar
An instance of URLClassLoader will be used to fetch class Foo. When Foo needs the definition of Baz, that same loader will be used to get Baz.
A jar file (or a directory on your local drive) can contain anything at all, not just .class files. It might contain .prioperties files. These are called "resources". If you bundle them up with your class files, then the class loader that loaded the class files can also get them. So if your widget has gif files that it uses for icons, you just bundle them all up together.
Of course, Class.getResource() is just a convenience method for Class.getClassLoader().getResource().