employ.java

静态方法读取每条Employee记录。将writeFixedString和readFixedString方法放入DataIO辅助类中

package Employman;

import java.util.*;
//import java.io.BufferedReader;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
//import java.io.FileReader;
//import java.io.FileWriter;
import java.io.IOException;
//import java.io.PrintWriter;
import java.io.RandomAccessFile;

//import Employman.Employee;

public class Employ {

	/**
	 * @param args
	 */
	public static void main(String[] args) 
	{
		// TODO Auto-generated method stub

		Employee[] staff=new Employee[3];
		
		staff[0]=new Employee("CC",7500,1987,12,15);
		staff[1]=new Employee("HH",5000,1989,10,1);
		staff[2]=new Employee("TT",4000,1990,3,15);
		
		try
		{
			//save all employee records to the file employee.dat
			DataOutputStream out=new DataOutputStream(new FileOutputStream("C:\\Documents and Settings\\123\\workspace\\homework\\src\\Employman\\employee.dat"));
			for(Employee e:staff)
				e.writeData(out);
			out.close();
			
			//retrieve all records into a new arry
			RandomAccessFile in=new RandomAccessFile("C:\\Documents and Settings\\123\\workspace\\homework\\src\\Employman\\employee.dat","r");
			//compute the array size
			int n=(int)(in.length()/Employee.RECORD_SIZE);
			Employee[] newStaff=new Employee[n];
			
			//read employees in reverse order
			for(int i=n-1;i>=0;i--)
			{
				newStaff[i]=new Employee();
				in.seek(i*Employee.RECORD_SIZE);
				newStaff[i].readData(in);
			}
			in.close();
			
				
			//print the newly read employee records
			for(Employee e:newStaff)
				System.out.println(e);
				
			}catch(IOException e)
			{
				e.printStackTrace();
			}
		}
	}
    class Employee
    {
    	public String name;
    	private double salary;
    	private Date hireDay;
    	
    	public static final int NAME_SIZE=40;
    	public static final int RECORD_SIZE=2*NAME_SIZE+8+4+4+4;
    	
    	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;
    	}
    	
    	/*
    	 * write employee data to a data output
    	 * param out the data output
    	 * */
    	public void raiseSalary(double byPercent)
    	{
    		double raise=salary*byPercent/100;
    		salary+=raise;
    	}
    	
    	public String toString()
    	{
    		return getClass().getName()
    		+"[name="+name
    		+",salary="+salary
    		+",hirDay"+hireDay
    		+"]";
    	}
    	/*
    	 * write emloyee data to a data output
    	 * param out the data output
    	 * */
    	
    	public void writeData(DataOutput out) throws IOException
    	{
    		DataIO.writeFixedString(name,NAME_SIZE,out);
    		out.writeDouble(salary);
    		
    		GregorianCalendar calendar=new GregorianCalendar();
    		calendar.setTime(hireDay);
    		out.writeInt(calendar.get(Calendar.YEAR));
    		out.writeInt(calendar.get(Calendar.MONTH)+1);
    		out.writeInt(calendar.get(Calendar.DAY_OF_MONTH));
    		
    	}
    	 /*
    	 Read employee data from a data input
    	 param n the data input
    	 */
    	public void readData(DataInput in) throws IOException
    	{
    		name=DataIO.readFixedString(NAME_SIZE,in);
    		salary=in.readInt();
    		int y=in.readInt();
    		int m=in.readInt();
    		int d=in.readInt();
    		GregorianCalendar calendar=new GregorianCalendar(y,m-1,d);
        	hireDay=calendar.getTime();
    	}
    }
    class DataIO
    {
    	public static String readFixedString(int size,DataInput in)
    	throws IOException
    	{
    		StringBuilder b=new StringBuilder(size);
    		int i=0;
    		boolean more=true;
    		while(more&&i<size)
    		{
    			char ch=in.readChar();
    			i++;
    			if(ch==0)more=false;
    			else b.append(ch);
    		}
    		in.skipBytes(2*(size-i));
    		return b.toString();
    	}
    	public static void writeFixedString(String s,int size,DataOutput out)
    	throws IOException
    	{
    		int i;
    		for(i=0;i<size;i++)
    		{
    			char ch=0;
    			if(i<s.length())ch=s.charAt(i);
    			out.writeChar(ch);
    		}
    	}
    }