binaryfilereadwrite.java

国外的数据结构与算法分析用书

package sequentialProcessing;

import java.io.*;
import java.util.StringTokenizer;
import dslib.file.ObjectFileUos;

/**	Read the data for a sequence of employees from a text file, 
	write it into a binary file, and then read the binary file 
	to calculate and print the average hourly wage.  */

public class BinaryFileReadWrite
{
	/**	Create and process a master file. <br>
		Analysis: Time = O(n) file reads and writes, n = the number of employees */
	public BinaryFileReadWrite() throws Exception
	{
		createMasterFile();
		processMasterFile();
	}

	/**	Read data from a text file to create a master binary file.  <br>
		Analysis: Time = O(n) file reads and writes, n = the number of employees */
	public void createMasterFile() throws Exception
	{
		BufferedReader inFile = new BufferedReader(new FileReader("employeeList.dat")); 
		ObjectFileUos masterFile = new ObjectFileUos("masterFile", "rw");
		masterFile.wipeOut();

		String empName = inFile.readLine();
		while (empName != null)
		{
			StringTokenizer tokenFinder = new StringTokenizer (inFile.readLine());
			int empNumber = Integer.parseInt(tokenFinder.nextToken());
			float empRate = Float.parseFloat(tokenFinder.nextToken());
			String empClass = tokenFinder.nextToken();
			Employee emp = new Employee(empName, empNumber, empRate, empClass);
			masterFile.writeObject(emp);
			empName = inFile.readLine();
		}
		inFile.close();
		masterFile.close();
	}

	/**	Read employees from a binary file, and compute and print the average hourly rate.  <br>
		Analysis: Time = O(n) file reads, n = the number of employees */
	public void processMasterFile() throws Exception
	{
		ObjectFileUos masterFile = new ObjectFileUos("masterFile", "r");
		int count = 0;
		float total = 0;
		while (!masterFile.eof())
		{
			Employee emp = (Employee) masterFile.readObject();
			System.out.println(emp);
			count++;
			total += emp.rate;
		}
		System.out.println("The average hourly rate is " + total/count);
		masterFile.close();
	}

	public static void main(String[] args) throws Exception
	{
		BinaryFileReadWrite ts = new BinaryFileReadWrite();
	}
}