使用类的静态变量和构造方法，可以跟踪某个类创建的对象个数。声明一个图书类，数据成员为编号，书名，书价，并拥有静态数据成员册数记录图书的总数。图书编号从1000开始， 每产生一个对象，则编号自动递增（

package b;
class Book{
private int bookId;
private String bookName;
private double price;
private static int ZS;
private static int BH;
static{
ZS=0;
BH=1000;
}
public Book(String bookName,double price){
  this.bookName=bookName;
  this.price=price;
  bookId=BH;
  inZH();
  inHAO();
}
public int getBookId() {
  return bookId;
}
public void setBookId(int bookId) {
  this.bookId = bookId;
}
public String getBookName() {
  return bookName;
}
public void setBookName(String bookName) {
  this.bookName = bookName;
}
public double getPrice() {
  return price;
}
public void setPrice(double price) {
  this.price = price;
} 
static void inZH(){
  ZS++;
}
static void inHAO(){
  BH++;
}
public static int HAOMA(){
  return BH-1000;
}
public String toString(){
  return "书号"+this.getBookId()+"书名"+this.getBookName()+"价格为"+this.getPrice();
}
}
public class b{
public static void main(String args[]){
 Book[] books = {
  new Book("c语言程序设计",45),
  new Book("数据结构与算法（c语言）",38),
  new Book("Java程序设计 实例操作",59.8)};
 System.out.println("图书总数为："+ Book.HAOMA());
 for(Book b:books){
  System.out.println(b.toString());
  }
 }
}