对于几百M或上G的大文件可使用java nio进行读写 ， 根据个人的需求 可能需要将一个超大文件读写形成很多较小的文件进行分析，这也不是什么难事，在读完一个缓冲区后 更换写入的对象即可，本文就不做详细介绍了，有需要的可以联系本人。

直接上程序吧

package cn.gzu.readfile; import java.io.File; import java.io.IOException; import java.io.RandomAccessFile; import java.nio.ByteBuffer; import java.nio.channels.FileChannel; public class ReadWriteNio { public static void main(String args[]) throws Exception{ int bufSize = 100; File fin = new File("E:\\jiahui\\2014-09-01.dat"); File fout = new File("E:\\jiahui\\res.txt"); System.out.print("开始读取并重写文件，请等待..."); 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("读写完成！"); } 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(rBuffer)) != -1){ // while(fcin.read(rBuffer) != -1){ if(size > 1*1024){ break; } int rSize = rBuffer.position(); rBuffer.rewind(); rBuffer.get(bs); rBuffer.clear(); String tempString = new String(bs, 0, rSize,"UTF-8"); // System.out.println(size+": "+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 + "\n"); System.out.println(size+": "+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(); } } }

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。