java实现超大文件的读写功能
作者：只要你能好
这篇文章主要为大家详细介绍了java实现超大文件的读写功能，具有一定的参考价值，感兴趣的小伙伴们可以参考一下
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！");
}
/*读文件同时写文件*/
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();
}
}
/*写文件*/
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脚本之家。