java - 将父类实例对象转换为子类实例对象的行为

Question

假设我有一个类如下:

private class ComparableElement extends Element implements Comparable<ComparableElement> {

        @Override
        public int compareTo(ComparableElement o) {
            return getName().compareTo(o.getName());
        }
    }

其中 Elements 定义如下:

public class Element {

    protected String name;

    protected String category;

    public Element() {
        super();
    }

    public Element(String _name, String _category) {
        super();
        this.name = _name;
        this.category = _category;
    }

    public String getName() {
        return name; 
    }
}

那么，如果我有一个 Element 对象，将该 Element 对象转换为 ComparableElement 实例的最佳实践是什么？类似的东西:

Element e;
...
ComparableElement ce = (ComparableElement)e;

只是这行不通......

Answer 1

您可以创建新的构造器ComparableElement:

public ComparableElement (Element element )
{

     //Here you get all the data from the element and set it to this object.

}