자바 부모 자식클래스 형변환 질문드립니다.

import java.awt.*;
import javax.swing.*;
import java.util.*;
 
 
public class CParent
{
    Object o;
 
    public CParent()
    {
    }
 
    public void fn()
    {
	System.out.println("fn()");
    }
}
 
 
 
import java.awt.*;
import javax.swing.*;
import java.util.*;
 
public class COther
{
    public COther()
    {
    }
 
    public void fnOther()
    {
	System.out.println("fnOther()");
    }
}
 
 
 
 
import java.awt.*;
import javax.swing.*;
import java.util.*;
 
 
class Child extends CParent
{
    public Child ()
    {
    }
 
    public static void main(String[] args)
    {
	Child c = new Child();
        c.fn();
 
	COther co = new COther();
	c.o = (Object) co;
	((COther)c.o).fnOther();
    }
}
 
 
 
javac CParent.java
javac COther.java
javac Child.java
java Child
pause
 
 
C:\Documents and Settings\shint\바탕 화면\>javac CParent.java
 
C:\Documents and Settings\shint\바탕 화면\>javac COther.java
 
C:\Documents and Settings\shint\바탕 화면\>javac Child.java
 
C:\Documents and Settings\shint\바탕 화면\>java Child
fn()
fnOther()
 
C:\Documents and Settings\shint\바탕 화면\>pause
 
계속하려면 아무 키나 누르십시오 . . .