NIO 读写

package com.chah.io;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:\\tmp\\logs\\qyh-CC.log");// 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);readFileByLine(bufSize, fcin, rBuffer, null, 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();}}}