java使用多线程读取超大文件

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.Observable;
 
/**
 * Created with IntelliJ IDEA.
 * User: okey
 * Date: 14-4-2
 * Time: 下午3:12
 * 读取文件
 */
public class ReadFile extends Observable {
 
 private int bufSize = 1024;
 // 换行符
 private byte key = "\n".getBytes()[0];
 // 当前行数
 private long lineNum = 0;
 // 文件编码,默认为gb2312
 private String encode = "gb2312";
 // 具体业务逻辑监听器
 private ReaderFileListener readerListener;
 
 public void setEncode(String encode) {
 this.encode = encode;
 }
 
 public void setReaderListener(ReaderFileListener readerListener) {
 this.readerListener = readerListener;
 }
 
 /**
 * 获取准确开始位置
 * @param file
 * @param position
 * @return
 * @throws Exception
 */
 public long getStartNum(File file, long position) throws Exception {
 long startNum = position;
 FileChannel fcin = new RandomAccessFile(file, "r").getChannel();
 fcin.position(position);
 try {
  int cache = 1024;
  ByteBuffer rBuffer = ByteBuffer.allocate(cache);
  // 每次读取的内容
  byte[] bs = new byte[cache];
  // 缓存
  byte[] tempBs = new byte[0];
  String line = "";
  while (fcin.read(rBuffer) != -1) {
  int rSize = rBuffer.position();
  rBuffer.rewind();
  rBuffer.get(bs);
  rBuffer.clear();
  byte[] newStrByte = bs;
  // 如果发现有上次未读完的缓存,则将它加到当前读取的内容前面
  if (null != tempBs) {
   int tL = tempBs.length;
   newStrByte = new byte[rSize + tL];
   System.arraycopy(tempBs, 0, newStrByte, 0, tL);
   System.arraycopy(bs, 0, newStrByte, tL, rSize);
  }
  // 获取开始位置之后的第一个换行符
  int endIndex = indexOf(newStrByte, 0);
  if (endIndex != -1) {
   return startNum + endIndex;
  }
  tempBs = substring(newStrByte, 0, newStrByte.length);
  startNum += 1024;
  }
 } catch (Exception e) {
  e.printStackTrace();
 } finally {
  fcin.close();
 }
 return position;
 }
 
 /**
 * 从设置的开始位置读取文件，一直到结束为止。如果 end设置为负数,刚读取到文件末尾
 * @param fullPath
 * @param start
 * @param end
 * @throws Exception
 */
 public void readFileByLine(String fullPath, long start, long end) throws Exception {
 File fin = new File(fullPath);
 if (fin.exists()) {
  FileChannel fcin = new RandomAccessFile(fin, "r").getChannel();
  fcin.position(start);
  try {
  ByteBuffer rBuffer = ByteBuffer.allocate(bufSize);
  // 每次读取的内容
  byte[] bs = new byte[bufSize];
  // 缓存
  byte[] tempBs = new byte[0];
  String line = "";
  // 当前读取文件位置
  long nowCur = start;
  while (fcin.read(rBuffer) != -1) {
   nowCur += bufSize;
 
   int rSize = rBuffer.position();
   rBuffer.rewind();
   rBuffer.get(bs);
   rBuffer.clear();
   byte[] newStrByte = bs;
   // 如果发现有上次未读完的缓存,则将它加到当前读取的内容前面
   if (null != tempBs) {
   int tL = tempBs.length;
   newStrByte = new byte[rSize + tL];
   System.arraycopy(tempBs, 0, newStrByte, 0, tL);
   System.arraycopy(bs, 0, newStrByte, tL, rSize);
   }
   // 是否已经读到最后一位
   boolean isEnd = false;
   // 如果当前读取的位数已经比设置的结束位置大的时候，将读取的内容截取到设置的结束位置
   if (end > 0 && nowCur > end) {
   // 缓存长度 - 当前已经读取位数 - 最后位数
   int l = newStrByte.length - (int) (nowCur - end);
   newStrByte = substring(newStrByte, 0, l);
   isEnd = true;
   }
   int fromIndex = 0;
   int endIndex = 0;
   // 每次读一行内容，以 key（默认为\n） 作为结束符
   while ((endIndex = indexOf(newStrByte, fromIndex)) != -1) {
   byte[] bLine = substring(newStrByte, fromIndex, endIndex);
   line = new String(bLine, 0, bLine.length, encode);
   lineNum++;
   // 输出一行内容，处理方式由调用方提供
   readerListener.outLine(line.trim(), lineNum, false);
   fromIndex = endIndex + 1;
   }
   // 将未读取完成的内容放到缓存中
   tempBs = substring(newStrByte, fromIndex, newStrByte.length);
   if (isEnd) {
   break;
   }
  }
  // 将剩下的最后内容作为一行，输出，并指明这是最后一行
  String lineStr = new String(tempBs, 0, tempBs.length, encode);
  readerListener.outLine(lineStr.trim(), lineNum, true);
  } catch (Exception e) {
  e.printStackTrace();
  } finally {
  fcin.close();
  }
 
 } else {
  throw new FileNotFoundException("没有找到文件：" + fullPath);
 }
 // 通知观察者,当前工作已经完成
 setChanged();
 notifyObservers(start+"-"+end);
 }
 
 /**
 * 查找一个byte[]从指定位置之后的一个换行符位置
 *
 * @param src
 * @param fromIndex
 * @return
 * @throws Exception
 */
 private int indexOf(byte[] src, int fromIndex) throws Exception {
 
 for (int i = fromIndex; i < src.length; i++) {
  if (src[i] == key) {
  return i;
  }
 }
 return -1;
 }
 
 /**
 * 从指定开始位置读取一个byte[]直到指定结束位置为止生成一个全新的byte[]
 *
 * @param src
 * @param fromIndex
 * @param endIndex
 * @return
 * @throws Exception
 */
 private byte[] substring(byte[] src, int fromIndex, int endIndex) throws Exception {
 int size = endIndex - fromIndex;
 byte[] ret = new byte[size];
 System.arraycopy(src, fromIndex, ret, 0, size);
 return ret;
 }
 
}

/**
 * Created with IntelliJ IDEA.
 * User: okey
 * Date: 14-4-2
 * Time: 下午4:50
 * To change this template use File | Settings | File Templates.
 */
public class ReadFileThread extends Thread {
 
 private ReaderFileListener processPoiDataListeners;
 private String filePath;
 private long start;
 private long end;
 
 public ReadFileThread(ReaderFileListener processPoiDataListeners,long start,long end,String file) {
 this.setName(this.getName()+"-ReadFileThread");
 this.start = start;
 this.end = end;
 this.filePath = file;
 this.processPoiDataListeners = processPoiDataListeners;
 }
 
 @Override
 public void run() {
 ReadFile readFile = new ReadFile();
 readFile.setReaderListener(processPoiDataListeners);
 readFile.setEncode(processPoiDataListeners.getEncode());
// readFile.addObserver();
 try {
  readFile.readFileByLine(filePath, start, end + 1);
 } catch (Exception e) {
  e.printStackTrace();
 }
 }
}

/**
 * Created with Okey
 * User: Okey
 * Date: 13-3-14
 * Time: 下午3:19
 * NIO逐行读数据回调方法
 */
public abstract class ReaderFileListener {
 
 // 一次读取行数，默认为500
 private int readColNum = 500;
 
 private String encode;
 
 private List list = new ArrayList();
 
 /**
 * 设置一次读取行数
 * @param readColNum
 */
 protected void setReadColNum(int readColNum) {
 this.readColNum = readColNum;
 }
 
 public String getEncode() {
 return encode;
 }
 
 public void setEncode(String encode) {
 this.encode = encode;
 }
 
 /**
 * 每读取到一行数据，添加到缓存中
 * @param lineStr 读取到的数据
 * @param lineNum 行号
 * @param over 是否读取完成
 * @throws Exception
 */
 public void outLine(String lineStr, long lineNum, boolean over) throws Exception {
 if(null != lineStr)
  list.add(lineStr);
 if (!over && (lineNum % readColNum == 0)) {
  output(list);
  list.clear();
 } else if (over) {
  output(list);
  list.clear();
 }
 }
 
 /**
 * 批量输出
 *
 * @param stringList
 * @throws Exception
 */
 public abstract void output(List stringList) throws Exception;
 
}

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
 
/**
 * Created with IntelliJ IDEA.
 * User: okey
 * Date: 14-4-1
 * Time: 下午6:03
 * To change this template use File | Settings | File Templates.
 */
public class BuildData {
 public static void main(String[] args) throws Exception {
 File file = new File("E:\\1396341974289.csv");
 FileInputStream fis = null;
 try {
  ReadFile readFile = new ReadFile();
  fis = new FileInputStream(file);
  int available = fis.available();
  int maxThreadNum = 50;
  // 线程粗略开始位置
  int i = available / maxThreadNum;
  for (int j = 0; j < maxThreadNum; j++) {
  // 计算精确开始位置
  long startNum = j == 0 ? 0 : readFile.getStartNum(file, i * j);
  long endNum = j + 1 < maxThreadNum ? readFile.getStartNum(file, i * (j + 1)) : -2;
  // 具体监听实现
  ProcessDataByPostgisListeners listeners = new ProcessDataByPostgisListeners("gbk");
  new ReadFileThread(listeners, startNum, endNum, file.getPath()).start();
  }
 } catch (IOException e) {
  e.printStackTrace();
 } catch (Exception e) {
  e.printStackTrace();
 }
 }
}