JavaNio 文件按行读写_JAVA_编程开发_程序员俱乐部

package alex;

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{

//String infile = "D:\\workspace\\test\\usagetracking.log";
//FileInputStream fin= new FileInputStream(infile);
//FileChannel fcin = fin.getChannel();

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);

System.out.print("OK!!!");
}

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);
      //System.out.print("<200>");

      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);
       //System.out.print("</over/>");
       //write to anthone file
       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();
}
}

}