JAVA之NIO按行读写大文件，完美解决中文乱码问题

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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