Question

我想得到一个子类的实例，但我总是得到父类实例可以任何人解释我为什么？根据XMLType ID我得到了孩子的实例（字符串或anyURI）等。但在某些情况下我需要子类实例。

代码::

public abstract class WSType 

    public final static WSType getInstance(int xmlTypeId) {
        switch (xmlTypeId) {
        case STRING: return WSStringType2.getInstance(); //**here i am always getting Parent class but  i am calling instance of WSStringType2.**
        case ANYURI: return WSAnyURIType2.getInstance();
        }
    }

    public final static WSType getInstance(int xmlTypeId, String data) throws XCallException {
        WSType wsData = WSType.getInstance(xmlTypeId); /**/calling happening Here**

  }

    }
public class WSStringType extends WSType {

    protected String m_data;


    public WSStringType() { m_data = "'"; }
    public WSStringType(String name){ m_data=name; }

    public static WSStringType getInstance() {
        return new WSStringType();
    }


}
class WSStringType2 extends WSStringType {

   public WSStringType2() { m_data = "'"; }
   public static WSStringType2 getInstance() {
        return new WSStringType2();
    }

   public WSStringType2(String newValue){
         super(newValue);
   }


}

Answer 1

getInstance(int xmlTypeId)的返回类型是WSType，它是父项。您可以简单地将其投放到WSStringType2，因为WSStringType2延伸WSStringType而WSStringType延伸WSType

WSType wt = WSType.getInstance(STRING);
WSStringType2 wt2 = null;
if (t instanceof WSStringType2) {
    wt2 = (WSStringType2) wt;
}

我总是得到父类的实例。但我需要一个孩子

1 个答案: