使用NIO按行读写文件readLine、writeLine

import java.io.BufferedReader; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.RandomAccessFile; import java.nio.ByteBuffer; import java.nio.channels.FileChannel; public class TestNio { public static void main(String args[]) throws Exception{ int bufSize = 100; File fin = new File("D:\\workspace\\test\\usagetracking.log"); File fout = new File("D:\\workspace\\test\\usagetracking2.log"); 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); public static void readFileByLine(int bufSize, FileChannel fcin, ByteBuffer rBuffer, FileChannel fcout, ByteBuffer wBuffer){ String enterStr = "\n"; try{ byte[] bs = new byte[bufSize]; int size = 0; StringBuffer strBuf = new StringBuffer(""); //while((size = fcin.read(buffer)) != -1){ while(fcin.read(rBuffer) != -1){       int rSize = rBuffer.position();       rBuffer.rewind();       rBuffer.get(bs);       rBuffer.clear();       String tempString = new String(bs, 0, rSize);       //System.out.print(tempString);       int fromIndex = 0;       int endIndex = 0;       while((endIndex = tempString.indexOf(enterStr, fromIndex)) != -1){        String line = tempString.substring(fromIndex, endIndex);        line = new String(strBuf.toString() + line);        //System.out.print(line);        writeFileByLine(fcout, wBuffer, line);               strBuf.delete(0, strBuf.length());        fromIndex = endIndex + 1;       }       if(rSize > tempString.length()){       strBuf.append(tempString.substring(fromIndex, tempString.length()));       }else{       strBuf.append(tempString.substring(fromIndex, rSize));       } } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public static void writeFileByLine(FileChannel fcout, ByteBuffer wBuffer, String line){ try { //write on file head //fcout.write(wBuffer.wrap(line.getBytes())); //wirte append file on foot fcout.write(wBuffer.wrap(line.getBytes()), fcout.size()); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }