Using factory to get an instance for calling a static method

[Jean-Christophe Blanchard]

Hi,

I want to use design pattern factory that will return a converter class.
This converter class will call a static method to convert a file from one format to another.

the factory is like that :

public class ConversionFileFactory {

	public static ConversionFile getInstance(FileFormat ff) {
		ConversionFile conversionFile = null;	
		if (ff == FileFormat.PDF ) {
			conversionFile = new ConversionPdf() ;
		}
                ...................
                .................. 
		return conversionFile ;
	}
	
}

After I get an instance of ConversionFile I just call a static method convert() to convert the file.
It works, I could be happy but I am not so satisfied because not so clean.

In fact, it is not clean to call a static method from an instance... so I would like to have something cleaner.

Do you know how can the factory return not an instance but a kind of Class so that I call the static method on a class and not on an instance ?

It cannot return a Class because the Class Class has no convert() method.

[Hunter McMillen]

There is a pretty informative article on Wikipedia about the Factory pattern, it has examples in Java.

http://en.wikipedia.org/wiki/Factory_method_pattern

Hunter

[Shawn Smith]

Is there a reason you have to return an instance variable? If you're trying to preserve how many converters exist and there's really no reason to return a handle to an instance you probably don't need to give an instance back to to the caller. In other words, something like:

public class ConversionEngine
{
   private static Map<String, Converter> converters_ = new HashMap<String, Converter>();

   public static void convert(Format format, File file)
   {
       if (!converters_.containsKey(format))
       {
           //build and instance and add to map
       }

       converters_.get(format).convert(file);
   }
}

Hopefully I'm understanding what you're trying to do.

Cheers,
Shawn

[Jean-Christophe Blanchard]

Thank you Shawn this method completely fit the needs.