定义一个Document类,有数据成员name,从Document派生Book类,增加数据成员pageCount。
private String name; //书名 public Document(String name) { this.name = name; } public String getName() { return name; } } public class Book extends Document{ private int pageCount; //页数 public Book(String name,int pageCount) { super(name); this.pageCount=pageCount; } public void display() { System.out.println("Name:"+getName()); System.out.println("PageCount:"+pageCount); } public static void main(String[] args) { Book b=new Book("Java",444); b.display(); } }
定义一个Object1类,有数据成员weight及相应的操作函数,由此派生出Box类,增加数据成员height和width及相应的操作函数,声明一个Box对象,观察构造函数的调用顺序。
class Object1{ private float weight; public Object1(float weight) { this.weight=weight; System.out.println("构造Object1类"); } public float getWeight() { return weight; } } public class Box extends Object1{ private float height; private float width; public Box(float weight,float height,float width) { super(weight); this.height=height; this.width=width; System.out.println("构造Box类"); } public void display() { System.out.println("The weight of the box is "+getWeight()); System.out.println("The height of the box is "+height); System.out.println("The width of the box is "+width); } public static void main(String[] args) { Box b=new Box(1.5554f,1,1.55f); b.display(); } }
三。例题