I have following class inheritances (A is my parent class):
In some cases, X and Y need some extra fields and methods. So what I basically need is this:
I don't want to extend X and Y to give their child classes exact the same fields and methods due to duplicate code.
How to handle this? Is the only solution a delegate?
Update: Real-world example:
I'm importing data from different file types:
Package my_application.core:
public class ImportFile { // the "A"
protected final Path path;
}
public class CsvImportFile extends ImportFile { // the "X"
private final String delimiter;
}
public class FixedLengthImportFile extends ImportFile { // the "Y"
// nothing new
}
public class XmlImportFile extends ImportFile {
private final String root;
}
Sometimes the first lines of a file contain heads/titles instead of data. So here an example extension which allows to set a start line for csv and fixed-length files:
Package my_application.extension.line_start:
public class ExtensionLineStartImportFile { // the "B"
protected final int lineStart;
// some methods
}
So if the user chooses to use the extension line_start, CsvImportFile and FixedLengthImportFile should get the properties of ExtensionLineStartImportFile.
Side node: Since I have multiple extensions which do different things and these extensions should be easy to add to/remove from the application, I don't want to merge them all into the "core".
