系统架构的蓝图——抽象类

abstract class Book_abst {
String name;
double price;
String author;
double sellPrice(double discount) {return price*discount;}
abstract void show();
}

class Book extends Book_abst {
void show(){
System.out.println("书名："+name);
System.out.println("定价："+price);
System.out.println("作者："+author);

}
}

class Execute {
public static void main (String[] args){
Book book1 = new Book();
book1.name="Thinking in Java";
book1.price=350.0;
book1.author="Bruce Eckel";
book1.show();
System.out.println("售价："+book1.sellPrice(0.8));

}
}