class A{
A(){
System.out.println("I am A!");
}
}class B extends A{
B(){
System.out.println("I am B!");
}
}class C extends B{
C(){
System.out.println("I am C!");
}
}class D extends C{
D(){
System.out.println("I am D!");
}
}public class csdn1
{
public static void main(String args[])
{
D d1=new D();
}
}
A(){
System.out.println("I am A!");
}
}class B extends A{
B(){
System.out.println("I am B!");
}
}class C extends B{
C(){
System.out.println("I am C!");
}
}class D extends C{
D(){
System.out.println("I am D!");
}
}public class csdn1
{
public static void main(String args[])
{
D d1=new D();
}
}
i am b
i am c
i am d
不知道对不对．
I am B!
I am C!
I am D!
I am A!
I am B!
I am C!
I am D!
所以b类有两个方法,c有三个，D有四个！在main方法中new了一个d类的具体对象d1,所以共输入4句：I am A!
I am B!
I am C!
I am D!
I am B!
I am C!
I am D!
子类继承父类，也继承了父类的构造方法