java 之动态绑定和静态绑定

package cn.lifx.test;  
 
public class Test   
{  
    public static void whichFoo(Base arg1, Base arg2)   
    {  
        arg1.foo(arg2);  
    }  
 
    public static void main(String[] args)   
    {  
        Base b = new Base();  
        Derived d = new Derived();  
 
        whichFoo(b, b);  
        whichFoo(b, d);  
        whichFoo(d, b);  
        whichFoo(d, d);  
    }  
}  
 
class Base   
{  
    public void foo(Base x)   
    {  
        System.out.println("Base.Base");  
    }  
 
    public void foo(Derived x)   
    {  
        System.out.println("Base.Derived");  
    }  
}  
 
class Derived extends Base   
{  
    public void foo(Base x)   
    {  
        System.out.println("Derived.Base");  
    }  
 
    public void foo(Derived x)   
    {  
        System.out.println("Derived.Derived");  
    }  
} 

package cn.lifx.test;

public class Test
{
public static void whichFoo(Base arg1, Base arg2)
{
arg1.foo(arg2);
}

public static void main(String[] args)
{
Base b = new Base();
Derived d = new Derived();

whichFoo(b, b);
whichFoo(b, d);
whichFoo(d, b);
whichFoo(d, d);
}
}

class Base
{
public void foo(Base x)
{
System.out.println("Base.Base");
}

public void foo(Derived x)
{
System.out.println("Base.Derived");
}
}

class Derived extends Base
{
public void foo(Base x)
{
System.out.println("Derived.Base");
}

public void foo(Derived x)
{
System.out.println("Derived.Derived");
}
}



输出为：

Java代码
Base.Base  
Base.Base  
Derived.Base  
Derived.Base 

Base.Base
Base.Base
Derived.Base
Derived.Base




如下面代码：

Java代码
package cn.lifx.test;  
 
public class Test   
{  
    public static void whichFoo(Base arg1, Base arg2)   
    {  
        arg1.foo(arg2);  
    }  
 
    public static void main(String[] args)   
    {  
        Base b = new Base();  
        Base base = new Derived();  
        Derived d = new Derived();  
          
        base.foo(b);  
        base.foo(d);  
        d.foo(b);  
        d.foo(base);  
          
        System.out.println();  
          
        whichFoo(b, b);  
        whichFoo(b, d);  
        whichFoo(d, b);  
        whichFoo(d, d);  
    }  
}  
 
class Base   
{  
    public void foo(Base x)   
    {  
        if(x instanceof Derived)  
        {  
            System.out.println("Base.Derived");  
        }  
        else if(x instanceof Base)  
        {  
            System.out.println("Base.Base");  
        }  
    }  
}  
 
class Derived extends Base   
{  
    public void foo(Base x)   
    {  
        if(x instanceof Derived)  
        {  
            System.out.println("Derived.Derived");  
        }  
        else if(x instanceof Base)  
        {  
            System.out.println("Derived.Base");  
        }  
    }  
} 

package cn.lifx.test;

public class Test
{
public static void whichFoo(Base arg1, Base arg2)
{
arg1.foo(arg2);
}

public static void main(String[] args)
{
Base b = new Base();
Base base = new Derived();
Derived d = new Derived();

base.foo(b);
base.foo(d);
d.foo(b);
d.foo(base);

System.out.println();

whichFoo(b, b);
whichFoo(b, d);
whichFoo(d, b);
whichFoo(d, d);
}
}

class Base
{
public void foo(Base x)
{
if(x instanceof Derived)
{
System.out.println("Base.Derived");
}
else if(x instanceof Base)
{
System.out.println("Base.Base");
}
}
}

class Derived extends Base
{
public void foo(Base x)
{
if(x instanceof Derived)
{
System.out.println("Derived.Derived");
}
else if(x instanceof Base)
{
System.out.println("Derived.Base");
}
}
} 

输出为：

Java代码
Derived.Base  
Derived.Derived  
Derived.Base  
Derived.Derived  
 
Base.Base  
Base.Derived  
Derived.Base  
Derived.Derived