Java的继承语法里的constructor

hoog

很久没有写java程序了，好多地方都忘了。这个程序给出的提示是，派生类生成时将自动调用基类的构造函数。而当基类与派生类拥有同样的成员变量时，须通过显示类型转换得以从派生类访问基类的同名成员变量。

//File Name : test.java
//Description: Test Derived class.When the derived class invoke the constructor function.
//      The constructor will invoke the base class constructor firstly.The other thing
//      should be realized is that we should use a type-cast method to get the field
//      member which the derived and base class both has.
//Author: Xie Jiancong
//Date: 2006.3.20
class A
{
private int cc ;
protected int ff;
public A(){
  System.out.println("A");
  cc = 10;
  ff = 11;
}
public void print(){
  System.out.println(cc);
}
}
class B extends A
{
private int dd ;
protected int ff ;
public B(){
  System.out.println("B");
  dd = 12;
  ff = 13;
}
public void print(){
  System.out.println(dd);
}
}
public class testDerived {
public static void main(String []args){
  B b = new B();
  A a = b;
  System.out.println(b.ff);  //Note here
  System.out.println(a.ff);  //
}
}

输出：
A
B
13
11



本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u/15509/showart_88326.html