Question

This is something that I was wondering how to do, but could not find a way that suits the problem.

Suppose I have a class that could serve two purposes: Upload and Download. Instinctively, I would create an object somewhat like this:

public class File{
 private FormFile uploadFile;
 private File downloadFile;
 private String uploadLocation;
 private String downloadLocation;

 //setters and getters
}

The thing is, I would want to have only one set of accessors for each type. For example, there is only one setFile(Object obj) in the class. But this would cause a problem because FormFile and File are two distinct objects.

I would then resort for OOP. Change my object to:

public interface File{
 public void setFile(Object obj);
 public Object getFile();
 public void setLocation;
 public String getLocation;
}

Then create the two other objects:

public UploadFile implements File{
 private FormFile file;
 private String location;

 //implementation of methods
}

public Download implements File{
 private File file;
 private String location;

 //implementation of methods
}

This could work if you clean other things within the code. But I realized that this would be harder to maintain afterwards. Is there another workaround to do this?

Something like:

File file = new File.UPLOAD;

would restrict the user to:

Use only method setFile(FileForm file){ }, and then setFile(File file){ } would become unavailable. Works vice versa when instantiating File file = new File.DOWNLOAD

I’m not really trying to solve anything on this. Just a thought.

Answer 1

Try with generics:

public class File < T > {

    private T file;
    private String location;

    public T getFile() {
        return file;
    }
    public void setFile( T file ) {
        this.file = file;
    }

    public String getLocation() {
        return location;
    }
    public void setLocation( String location ) {
        this.location = location;
    }

}

Usage:

File< FormFile > uploadFile = new File< FormFile >();
uploadFile.setFile( new FormFile() );

File< java.io.File > downloadFile = new File< java.io.File >();
downloadFile.setFile( new java.io.File( "something.txt" ) );