[jdjlist] Re: casting problem (maybe)

[Darryl Patterson]

Yes indeed it will call the method from the child. This is due to a 
feature called dynamic method binding. Java will dynamically bind a 
method call to the child  object furthest down the class heirarchy. So:

class ParentClass {
   public void callMethod(){
       System.out.println("The Parent");
   }
}
class ChildClass extends ParentClass {
   public void callMethod(){
       System.out.println("The Child");
   }
}
class Test {
   public static void main(String[] args){
       ParentClass example1 = new ChildClass();
       example1.callMethod(); // will call the method in ChildClass
       ((ParentClass)example1).callMethod(); // will still call the 
method in ChildClass

       ParentClass example2 = new ParentClass();
       example2.callMethod(); // will call method in ParentClass, as 
that is the furthest child down the heirarchy in the variable example2
   }
}

Hope that helps explain why.
D
Luc Foisy wrote:

If I cast an object as its superclass, then call a method that has been overrided 
in the child, will it call the method from the child or the superclass??
Such as:

public class TMHTTPDataObject
{
        String value = "";
        public void setValue(String _value)
        {
                value = _value;
        }
        public String getValue()
        {
                return value;
        }
}
public class TMHTTPDateField
{
        public void setValue(String _value)
        {
                value = dateConvert(_value);
        }
}
if( panelItems.elementAt(i) instanceof TMHTTPDataObject )
{
        TMHTTPDataObject temp = (TMHTTPDataObject) panelItems.elementAt(i);
        if( temp.getLinkedField().equals(_linkedField) )
        {
                temp.setValue(_value);
                break;
        }
}
Should getValue return the string straight up or the dateConverted string??

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