package com.chillax.imp;

import java.io.File;


import java.io.IOException;


import java.io.RandomAccessFile;


import java.nio.ByteBuffer;


import java.nio.channels.FileChannel;


import java.util.ArrayList;


import java.util.Date;


import java.util.List;

/**
NIO读取百万级别文件
@author Chillax

*/


public class NIO {
public static void main(String args[]) throws Exception {

	int bufSize = 1000000;//一次读取的字节长度

	File fin = new File("D:\\test\\20160622_627975.txt");//读取的文件

	File fout = new File("D:\\test\\20160622_627975_1.txt");//写出的文件

	Date startDate = new Date();

	FileChannel fcin = new RandomAccessFile(fin, "r").getChannel();

	ByteBuffer rBuffer = ByteBuffer.allocate(bufSize);

	FileChannel fcout = new RandomAccessFile(fout, "rws").getChannel();

	ByteBuffer wBuffer = ByteBuffer.allocateDirect(bufSize);

	readFileByLine(bufSize, fcin, rBuffer, fcout, wBuffer);

	Date endDate = new Date();

	System.out.print(startDate+"|"+endDate);//测试执行时间

	if(fcin.isOpen()){

		fcin.close();

	}

	if(fcout.isOpen()){

		fcout.close();

	}

}

public static void readFileByLine(int bufSize, FileChannel fcin,

		ByteBuffer rBuffer, FileChannel fcout, ByteBuffer wBuffer) {

	String enter = "\n";

	List<String> dataList = new ArrayList<String>();//存储读取的每行数据

	byte[] lineByte = new byte[0];

	String encode = "GBK";


//		String encode = "UTF-8";


try {


//temp：由于是按固定字节读取，在一次读取中，第一行和最后一行经常是不完整的行，因此定义此变量来存储上次的最后一行和这次的第一行的内容，


//并将之连接成完成的一行，否则会出现汉字被拆分成2个字节，并被提前转换成字符串而乱码的问题


byte[] temp = new byte[0];


while (fcin.read(rBuffer) != -1) {//fcin.read(rBuffer)：从文件管道读取内容到缓冲区(rBuffer)


int rSize = rBuffer.position();//读取结束后的位置，相当于读取的长度


byte[] bs = new byte[rSize];//用来存放读取的内容的数组


rBuffer.rewind();//将position设回0,所以你可以重读Buffer中的所有数据,此处如果不设置,无法使用下面的get方法


rBuffer.get(bs);//相当于rBuffer.get(bs,0,bs.length())：从position初始位置开始相对读,读bs.length个byte,并写入bs[0]到bs[bs.length-1]的区域


rBuffer.clear();
			int startNum = 0;

			int LF = 10;//换行符

			int CR = 13;//回车符

			boolean hasLF = false;//是否有换行符

			for(int i = 0; i < rSize; i++){

				if(bs[i] == LF){

					hasLF = true;

					int tempNum = temp.length;

					int lineNum = i - startNum;

					lineByte = new byte[tempNum + lineNum];//数组大小已经去掉换行符

					System.arraycopy(temp, 0, lineByte, 0, tempNum);//填充了lineByte[0]~lineByte[tempNum-1]

					temp = new byte[0];

					System.arraycopy(bs, startNum, lineByte, tempNum, lineNum);//填充lineByte[tempNum]~lineByte[tempNum+lineNum-1]

					String line = new String(lineByte, 0, lineByte.length, encode);//一行完整的字符串(过滤了换行和回车)

					dataList.add(line);


//						System.out.println(line);


writeFileByLine(fcout, wBuffer, line + enter);
					//过滤回车符和换行符

					if(i + 1 < rSize && bs[i + 1] == CR){

						startNum = i + 2;

					}else{

						startNum = i + 1;

					}

				}

			}

			if(hasLF){

				temp = new byte[bs.length - startNum];

				System.arraycopy(bs, startNum, temp, 0, temp.length);

			}else{//兼容单次读取的内容不足一行的情况

				byte[] toTemp = new byte[temp.length + bs.length];

				System.arraycopy(temp, 0, toTemp, 0, temp.length);

				System.arraycopy(bs, 0, toTemp, temp.length, bs.length);

				temp = toTemp;

			}

		}

		if(temp != null && temp.length > 0){//兼容文件最后一行没有换行的情况

			String line = new String(temp, 0, temp.length, encode);

			dataList.add(line);


//				System.out.println(line);


writeFileByLine(fcout, wBuffer, line + enter);


}


} catch (IOException e) {


e.printStackTrace();


}


}
/**

 * 写到文件上

 * @param fcout

 * @param wBuffer

 * @param line

 */

@SuppressWarnings("static-access")

public static void writeFileByLine(FileChannel fcout, ByteBuffer wBuffer,

		String line) {

	try {

		fcout.write(wBuffer.wrap(line.getBytes("UTF-8")), fcout.size());

	} catch (IOException e) {

		e.printStackTrace();

	}

}


}

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