java多线程读写文件

一、引言

    使用java读写文件是日常工作中需要经常使用的技术。为了提高文件写出分析和写出效率，本文采用多线程实现多文件解析和写出。具体实现如下：

二、文件读写工具类

package com.test.multiThreadsReadFile.utils;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.univocity.parsers.csv.CsvWriter;
import com.univocity.parsers.csv.CsvWriterSettings;

/**
 * @author admin 文件读写工具类
 */
public class FileUtil
{
	/**
	 * 读取txt文件工具类
	 * @param inputPath
	 * @return
	 */
	public static Map> readTxtFile(String inputPath)
	{
		Map> map = new HashMap>();
		List aList = new ArrayList();
		List bList = new ArrayList();
		List cList = new ArrayList();
		BufferedReader reader = null;
		try
		{
			reader = new BufferedReader(new InputStreamReader(  
	                new FileInputStream(inputPath), "UTF-8"),10*1024*1024);
			String line = "";
			while((line = reader.readLine()) != null)
			{
				if(null == line || line.isEmpty())
				{
					continue;
				}
				String[] split = line.split("=");
				if(split.length < 2)
				{
					continue;
				}
				if(split[0].equals("a"))
				{
					aList.add(split[1]);
				}
				if(split[0].equals("b"))
				{
					bList.add(split[1]);
				}
				if(split[0].equals("c"))
				{
					cList.add(split[1]);
				}
			}
			map.put("a", aList);
			map.put("b", bList);
			map.put("c", cList);
		} catch (FileNotFoundException e)
		{
			e.printStackTrace();
		} catch (UnsupportedEncodingException e)
		{
			e.printStackTrace();
		} catch (IOException e)
		{
			e.printStackTrace();
		}
		return map;
	}

	/**
	 * 写出CSV文件工具类
	 * 
	 * @param os
	 * @param headers
	 * @param rows
	 * @throws IOException
	 */
	public static void writerCSVFile(String outputPath, List headers, List rows,String prefixName)
	{
		String fileName = prefixName + ".csv";
		// 新建需要写出的文件
		File file = new File(outputPath,fileName);
		Writer writer = null;
		try
		{
			// 如果写出地址是个文件夹，创建新文件
			if (file.isDirectory())
			{
				file.createNewFile();
			}
			writer = new FileWriter(file, true);
			// 创建文件写出流
			// 创建CSV文件写出设置
			CsvWriterSettings setting = new CsvWriterSettings();
			// 写出文件，并可以追加
			CsvWriter csvwriter = new CsvWriter(writer, setting);
			// 写出文件标题
			csvwriter.writeHeaders(headers);
			// 写出文件内容
			csvwriter.writeRowsAndClose(rows);
		} catch (IOException e)
		{
			e.printStackTrace();
		} finally
		{
			try
			{
				if (null != writer)
				{
					// 关闭文件写出流
					writer.close();
				}
			} catch (IOException e)
			{
				e.printStackTrace();
			}
		}
	}
}

三、业务接口类

package com.test.multiThreadsReadFile.service;

/**
 * @author admin
 * 文件读写接口
 */
public interface IService
{
	/**
	 * 文件读取主方法
	 * @param inputPath
	 * @param outputPath
	 * @return
	 */
	long readFile(String inputPath,String outputPath);
}

四、业务实现类

package com.test.multiThreadsReadFile.service.impl;

import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import com.test.multiThreadsReadFile.service.IService;
import com.test.multiThreadsReadFile.utils.FileUtil;

public class TxtFileService implements IService
{

	/*
	 * 读取文件，开启线程主方法
	 */
	@Override
	public long readFile(String inputPath,String outputPath)
	{
		//统计解析成功条数
		long successNum = 0;
		//读取全部文件
		Map> readTxtFile = FileUtil.readTxtFile(inputPath);
		//解析成功条数统计
		Hashtable successCount = new Hashtable();
		//获取标题
		List head = getHead();
		//组装线程名字，既文件前缀
		String[] fileName =
		{ "a", "b", "c" };

		// 创建计数器
		// 构造参数传入的数量值代表的是latch.countDown()调用的次数
		CountDownLatch latch = new CountDownLatch(3);
		// 创建线程池，可以通过以下方式创建
		ExecutorService threadPool = Executors.newFixedThreadPool(3);
		for (int i = 0; i < fileName.length; i++)
		{
			threadPool.execute(new ReadTxtFileThread(readTxtFile, head, latch, fileName[i], successCount,outputPath));
		}
		try
		{
			// 阻塞当前线程，直到所有线程都执行完毕
			latch.await();
		} catch (InterruptedException e)
		{
			e.printStackTrace();
		} finally
		{
			//所有业务执行完毕，关闭线程池
			threadPool.shutdown();
		}
		//解析成功条数统计
		for (Long num : successCount.values())
		{
			successNum += num;
		}
		return successNum;
	}

	/**
	 * 组装文件表头
	 * @return
	 */
	private List getHead()
	{
		List head = new ArrayList();
		head.add("A1");
		head.add("A2");
		head.add("A3");
		return head;
	}

}

五、解析与写出文件线程

package com.test.multiThreadsReadFile.service.impl;

import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CountDownLatch;

import com.test.multiThreadsReadFile.utils.FileUtil;

/**
 * @author admin
 * 文件写出线程
 */
public class ReadTxtFileThread implements Runnable
{
	/**
	 * 读取来的数据
	 */
	private Map> allLines;
	
	/**
	 * 表头
	 */
	private List head;
	
	/**
	 * 线程计数
	 */
	private CountDownLatch latch;
	
	/**
	 * 线程name
	 */
	private String ThreadName;
	
	/**
	 * 文件写出地址
	 */
	private String outputPath;
	
	/**
	 * 统计
	 */
	private Hashtable successCount;

	public ReadTxtFileThread(Map> allLines, List head, CountDownLatch latch,
			String threadName, Hashtable successCount,String outputPath)
	{
		super();
		this.allLines = allLines;
		this.head = head;
		this.latch = latch;
		this.ThreadName = threadName;
		this.successCount = successCount;
		this.outputPath = outputPath;
	}


	@Override
	public void run()
	{
		//通过判断线程名字来决定执行那个线程
		String[] str = {"a","b","c"};
		for (String name : str)
		{
			if(name.equals(ThreadName))
			{
				writeTxtFile(name);
			}
		}
		//线程计数
		latch.countDown();
	}


	/**
	 * 解析并写出文件
	 * @param type
	 */
	private synchronized void writeTxtFile(String type)
	{
		//每个文件写出条数统计
		long sucNum = 0;
		//需要写出的行
		List rows = new ArrayList();
		//生成文件标题
		String prefixName = type + System.currentTimeMillis();
		//需要写出的文件的原始数据
		List list = allLines.get(type);
		//根据需求解析文件
		for (String line : list)
		{
			String[] split = line.split(",");
			rows.add(split);
		}
		//统计单个文件成功条数
		sucNum = rows.size();
		successCount.put(type, sucNum);
		//调用工具类，写出CSV文件
		FileUtil.writerCSVFile(outputPath, head, rows,prefixName);
	}
}

六、测试

package com.test.multiThreadsReadFile.test;

import com.test.multiThreadsReadFile.service.IService;
import com.test.multiThreadsReadFile.service.impl.TxtFileService;

/**
 * @author admin
 *	测试类
 */
public class MyTest
{
	public static void main(String[] args)
	{
		//读取文件地址
		String inputPath = "C:\\Users\\test\\Desktop\\demo.txt";
		//写出文件地址
		String outputPath = "C:\\Users\\test\\Desktop\\1\\";
		IService readTxt = new TxtFileService();
		long readFile = readTxt.readFile(inputPath, outputPath);
		System.out.println("成功解析" + readFile + "条数据");
	}
}

七、总结

    本文中文件的解析和写出采用了多线，如果可以起三个线程：一个线程读、一个线程解析、一个线程写，三个线程同时工作可以大大提高读写效率。欢迎评论探讨！

Copyright ©2018  hbgengfei11