第四次作业

public class Demo61 { 
public static void main(String[] args) { 

class Book { 
 private String name; 
 private  int id;
 private float price;
 private static int  num=3;
 private static int count =0; 
 public Book(){ 
 count++;   
 this.id = count;
 }
  public Book(int id){   
 this.id = id; 
 } 
  public int getId(){  
  return this.id;
  }
  public Book(String name,float price){  
  this.name = name; 
   this.price = price; 
   this.num = num; 
 }
  public void setName(String name){
 this.name = name;  
 }
  public String getName(){ 
  return this.name;
 } 
  public void setPrice(float price){ 
  this.price = price;
 }
  public float getPrice(){ 
  return this.price; 
 }
  public void setNum(int num){  
  this.num = num;
  }
  public int getNum(){ 
  return this.num; 
     }
 }
  public class Lake{
  public static void main(String args[]){
  Book book[] = new Book[6]; 
  book[0] = new Book("java教程  ",99.9f); 
  book[1] = new Book("java web教程",69.9f);
  book[2] = new Book("java EE教程",67.9f);  
  book[3] = new Book("android教程 ",56.8f);   
  book[4] = new Book("Mysql教程  ",56.5f);  
  book[5] = new Book("oracle教程",78.7f);  
    for (int i=0;i<book.length;i++ ){   
  System.out.println("编号："+new Book().getId()+"\t书名："+book[i].getName()+
      "\t价格："+book[i].getPrice()+"\t数量："+book[i].getNum());
    }
     System.out.println("图书总量为："+(new Book().getId()-1)*book[1].getNum());
       }
  }

String str1 = "Java技术学习班20070326"; 
System.out.println(str1.substring(9, 17)); 
String str2 = "MLDN Java"; 
System.out.println(str2.replaceAll("JAVA", "J2EE"));// 如果寻找的Java不在str2里面，则不替换 
String str3 = "Java技术学习班20070326"; 
System.out.println(str3.charAt(8)); 
String str4 = "Java技术学习班20070326"; 
System.out.println(str4.replace("0", "")); 
String str5 = "Java技术学习班   20070326   MLDN 老师"; 
System.out.println(str5.replace(" ", "")); 
String str6 = "320821199410055500"; 
System.out.println(str6.substring(6, 17)); 
} 
}