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<String> list = new ArrayList<String>();
 
 /**
  * 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<String> 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();
  }
 }
}