遵循Java代码行意味着什么

RenderingModel

RenderableDefinition

public class RenderingModelImpl < RD extends RenderableDefinition >  
    implements RenderingModel {

public class RenderingModelImpl < RD
extends RenderableDefinition >
implements RenderingModel {
    protected final RenderingModel parentModel;
    protected final Content content;
    protected final RD definition;

    public RenderingModelImpl(Content content, RD definition, RenderingModel
parent) {
        this.content = content;
        this.definition = definition;
        this.parentModel = parent;
    }

    public RenderingModel getParent() {
        return this.parentModel;
    }

    public RenderingModel getRoot(){
        RenderingModel model = this;
        while(model.getParent() != null){
            model = model.getParent();
        }
        return model;
    }

    public Content getContent() {
        return this.content;
    }

    /**
     * Shortname for templates: model.def.
     */
    public RD getDef() {
        return getDefinition();
    }

    public RD getDefinition() {
        return this.definition;
    }

    public String execute() {
        return null;
    }

}