Java对象，继承和接口(Java objects, inheritance and interface)

 我认为你真正需要的是工厂。 工厂是一个知道，如果有一些信息可以处理，如何创建必要的适当类型的对象。 在您的情况下，您将创建一个解析器接口，然后分离实现各种解析器的类。 最后，创建一个解析器工厂，它具有一定的能力来告诉创建哪种解析器，创建并返回所需的类型。 这就是你的逻辑。 工厂提供了一种本地化所创建项目的创建逻辑的方法。 
 
public interface IParser<T>
{
    T Parse<T>( string item );
}

public class KeyValueParser : IParser<KeyValue>
{
    KeyValuePair Parse<KeyValue>( string item );
}

...

public class ParserFactory
{
    public IParser<T> CreateParser<T>()
    {
        var type = typeof(T);
        if (type == typeof(KeyValuePair))
        {
            return new KeyValueParser();
        }
        ...
        throw new InvalidOperationException( "No matching parser type." );
    }
}
 
 其他一些人建议使用插件模型，如果合适，可以调整工厂以读取插件配置，加载适当的插件，并根据需要创建实例类型。 在这种情况下，将工厂视为“经理”可能更合适，因为它不仅仅是创建实例。 

I think what you're really needing is a Factory. A Factory is a class that knows, given some information to work on, how to create objects of the proper type necessary. In your case, You'd create a parser interface, then separate classes implementing various parsers. Finally, create a parser factory that, given some ability to tell which kind of parser to create, creates and returns the kind needed. This is where your logic would go. The Factory provides a way to localize the creational logic for the items being created.
 
public interface IParser<T>
{
    T Parse<T>( string item );
}

public class KeyValueParser : IParser<KeyValue>
{
    KeyValuePair Parse<KeyValue>( string item );
}

...

public class ParserFactory
{
    public IParser<T> CreateParser<T>()
    {
        var type = typeof(T);
        if (type == typeof(KeyValuePair))
        {
            return new KeyValueParser();
        }
        ...
        throw new InvalidOperationException( "No matching parser type." );
    }
}
 
Some others have suggested a plugin model and, if appropriate, the factory can be adapted to read a plugin configuration, load the appropriate plugins, and create the instance types as needed. In that case it might be more appropriate to think of the factory as a "manager" since it does more than simply create instances.