各位大哥大姐来看看哪！

Question

我这几个程序，有两个能写，但回读时就找不到文件，而另外两个却没有这个问题，小弟百思不得其解，请大哥大姐指导一下。

Answer 1

import java.io.*;
 import java.util.*;
public class DataFileTest
 {
    
    public static void main(String[] args) 
    {
       Employee[] staff=new Employee[3];
       
       staff[0]=new Employee("Carl Cracker",75000,1987,12,15);
       staff[1]=new Employee("Harry Hacker",50000,1989,10,1);
       staff[2]=new Employee("Tony Tester",40000,1990,3,15);
       
       try
       {
        PrintWriter out=new PrintWriter(new FileWriter("employee.dat"));
        writeData(staff,out);
        out.close();
       
        BufferedReader in=new BufferedReader(new FileReader("employee.dat"));
        Employee[] newStaff=readData(in);
        in.close();
        for(int i=0;i<newStaff.length;i++)
        System.out.println(newStaff[i]);
       }
       catch(IOException exception)
       {
        exception.printStackTrace();
       }
    }
    static void writeData(Employee[] e,PrintWriter out) throws IOException
    {
     out.println(e.length);
    
     for(int i=0;i<e.length;i++)
     e[i].writeData(out); 
    }
    static Employee[] readData(BufferedReader in)throws IOException
    {
     int n=Integer.parseInt(in.readLine());
    
     Employee[] e=new Employee[n];
     for(int i=0;i<n;i++)
     {
     e[i]=new Employee();
     e[i].readData(in);
     }
     return e;
    }
}
class Employee
{
public Employee()
{
}
public Employee(String n,double s,int year,int month,int day)
{
name=n;
salary=s;
GregorianCalendar calendar=new GregorianCalendar(year,month-1,day);
hireDay=calendar.getTime();
}
public String getName()
{
return name;
}
public double getSalary()
{
return salary;
}
public Date getHireDay()
{
return hireDay;
}
public void raiseSalary(double byPercent)
{
double raise=salary*byPercent/100;
salary+=raise;
}
public String toString()
{
return getClass().getName()+"[name="+name+".salary="+salary+".hireDay="+hireDay+"]";
}
public void writeData(PrintWriter out)throws IOException
{
GregorianCalendar calendar=new GregorianCalendar();
calendar.setTime(hireDay);
out.println(name+"|"+salary+"|"+calendar.get(Calendar.YEAR)+"|"+calendar.get(Calendar.DAY_OF_MONTH));
}
public void readData(BufferedReader in) throws IOException
{
String s=in.readLine();
StringTokenizer t=new StringTokenizer(s,"|");
name=t.nextToken();
salary=Double.parseDouble(t.nextToken());
int y=Integer.parseInt(t.nextToken());
int m=Integer.parseInt(t.nextToken());
int d=Integer.parseInt(t.nextToken());
GregorianCalendar calendar=new GregorianCalendar(y,m-1,d);
hireDay=calendar.getTime();
}
private String name;
private double salary;
private Date hireDay;
}

Answer 2

这是第二个
import java.io.*;
 import java.util.*;
 class Employee implements Serializable
 {
  public Employee()
  {
  }
  public Employee(String n,double s,int year,int month,int day)
  {
  name=n;
  salary=s;
  GregorianCalendar calendar=new GregorianCalendar(year,month-1,day);
  hireDay=calendar.getTime();
  }
  public String getName()
  {
  return name;
  }
  public double  getSalary()
  {
  return salary;
  }
  public Date getHireDay()
  {
  return hireDay;
  }
  public void raiseSalary(double byPercent)
  {
  double raise=salary*byPercent/100;
  salary+=raise;
  }
  public String toString()
  {
  return getClass().getName()+"[name="+name+",salary="+salary+",hireDay="+hireDay+"]";
  }
  private String name;
  private double salary;
  private Date hireDay;
 }
 class Manager extends Employee
 {
  public Manager(String n,double s,int year,int month,int day)
  {
  super(n,s,year,month,day);
  bonus=0;
  }
  public double getSalary()
  {
  double baseSalary=super.getSalary();
  return baseSalary+bonus;
  }
  public void setBonus(double b)
  {
  bonus=b;
  }
  public String toString()
  {
  return super.toString()+"[bonus="+bonus+"]";
  }
  private double bonus;
 }
public class ObjectFileTest
 {
    
    public static void main(String[] args) 
    {
       Manager boss=new Manager("Carl Cracker",80000,1987,12,15);
       boss.setBonus(5000);
       
       Employee[] staff=new Employee[3];
       
       staff[0]=boss;
       staff[1]=new Employee("Harry Hacker",50000,1989,10,1);
       staff[2]=new Employee("Tony Tester",40000,1990,3,15);
       
       try
       {
        ObjectOutputStream out=new ObjectOutputStream(new FileOutputStream("employee.dat"));
        out.writeObject(staff);
        out.close();
       
        ObjectInputStream in=new ObjectInputStream(new FileInputStream("employee.dat"));
        Employee[] newStaff=(Employee[])in.readObject();
        in.close();
       
        for(int i=0;i<newStaff.length;i++)
        System.out.println(newStaff[i]);
       }
       catch(Exception e)
       {
        e.printStackTrace();
       }
    }
}

Answer 3

三
import java.io.*;
 import java.util.*;
 class Employee implements Serializable
 {
  public Employee()
  {
  }
  public Employee(String n,double s,int year,int month,int day)
  {
  name=n;
  salary=s;
  GregorianCalendar calendar=new GregorianCalendar(year,month-1,day);
  hireDay=calendar.getTime();
  }
  public String getName()
  {
  return name;
  }
  public double  getSalary()
  {
  return salary;
  }
  public Date getHireDay()
  {
  return hireDay;
  }
  public void raiseSalary(double byPercent)
  {
  double raise=salary*byPercent/100;
  salary+=raise;
  }
  public String toString()
  {
  return getClass().getName()+"[name="+name+",salary="+salary+",hireDay="+hireDay+"]";
  }
  private String name;
  private double salary;
  private Date hireDay;
 }
 class Manager extends Employee
 {
  public Manager(String n,double s,int year,int month,int day)
  {
  super(n,s,year,month,day);
  bonus=0;
  secretary=null;
  }
  public void setSecretary(Employee s)
  {
  secretary=s;
  }
  public double getSalary()
  {
  double baseSalary=super.getSalary();
  return baseSalary+bonus;
  }
  public void setBonus(double b)
  {
  bonus=b;
  }
  public String toString()
  {
  return super.toString()+"[bonus="+bonus+"]"+"[secretary="+secretary+"]";
  }
  private double bonus;
  private Employee secretary;
 }
public class ObjectRefTest 
{
    
    public static void main(String[] args) 
    {
        Employee harry=new Employee("Carl Cracker",50000,1989,10,1);
        Manager boss=new Manager("Carl Cracker",80000,1987,12,15);
        boss.setSecretary(harry);
        
        Employee[] staff=new Employee[3];
        staff[0]=boss;
        staff[1]=harry;
        staff[2]=new Employee("Tony Tester",40000,1990,1,15);
        try
        {
         ObjectOutputStream out =new ObjectOutputStream(new FileOutputStream("employee.dat"));
         out.writeObject(staff);
         out.close();
        
            ObjectInputStream in=new ObjectInputStream(new FileInputStream("employee.dat"));
            Employee[] newStaff=(Employee[])in.readObject();
            in.close();
            
            newStaff[1].raiseSalary(10);
            
            for(int i=0;i<newStaff.length;i++)
            System.out.println(newStaff[i]);
        }
        catch (Exception e)
        {
         e.printStackTrace();
        }
    }
}