一、多态的缺陷

1、覆盖私有方法

public class PrivateOverride{
private void f(){
print("private f()");
}
public static void main(String args[]){
PrivateOverride po=new Derived();
po.f();
}
}

class Derived extends PrivateOverride{
public void f(){
print("public f()");
}

}

private f()

2、如果某个方法为static，则它的行为不具有多态性

class StaticSuper{

public static void staticGet(){

	System.out.println("base staticGet()");

}

public void dynamicGet(){

	System.out.println("base dynamicGet()");

}

}

class StaticSub extends StaticSuper{

public static void staticGet(){

System.out.println("sub staticGet()");

}

public void dynamicGet(){

	System.out.println("sub dynamicGet()");

}

}

public class StaticPolymorphism{

public static void main(String args[]){

StaticSuper sup=new StaticSub();

sup.staticGet();

sup.dynamicGet();

}

}

output：

base staticGet()
sub dynamicGet()

二、构造器内部的多态方法的行为

class Glyph{
void draw(){print("Glyph.draw()");}
Glyph(){
print("Glyph before draw()");
draw();
print("Glyph after draw()");
}
}

class RoundGlyph extends Glyph{
private int radius=1;
RoundGlyph(r){
radius=r;
print("RoundGlyph.RoungGlyph(),radius="+radius);
}
void draw(){print("RoundGlyph.draw(),radius="+radius);}
}

public class PolyConstructors{
public static void main(String args[]){
new RoundGlyph(5);
}
}

Glyph before draw()

RoundGlyph.draw(),radius=0

Glyph after draw()

RoundGlyph.RoundGlyph(),radius=0