import org.apache.log4j.LogManager;import org.apache.log4j.Logger; import java.io.*;import java.util.*;import java.util.concurrent.*; public class FileSplitUtil {   private final static Logger log = LogManager.getLogger(FileSplitUtil.class);  private static final long originFileSize = 1024 * 1024 * 100;// 100M  private static final int blockFileSize = 1024 * 1024 * 64;// 防止中文亂碼，必須取2的N次方  /**   * CVS文件分隔符   */  private static final char cvsSeparator = '^';  public static void main(String args[]){    long start = System.currentTimeMillis();    try {      String fileName = "D://csvtest//aa.csv";      File sourceFile = new File(fileName);      if (sourceFile.length() >= originFileSize) {        String cvsFileName = fileName.replaceAll("http:////", "/");        FileSplitUtil fileSplitUtil = new FileSplitUtil();        List<String> parts=fileSplitUtil.splitBySize(cvsFileName, blockFileSize);        for(String part:parts){          System.out.println("partName is:"+part);        }      }      System.out.println("總文件長度"+sourceFile.length()+",拆分文件耗時:" + (System.currentTimeMillis() - start) + "ms.");    }catch (Exception e){      log.info(e.getStackTrace());    }   }     /**   * 拆分文件   *   * @param fileName 待拆分的完整文件名   * @param byteSize 按多少字節大小拆分   * @return 拆分后的文件名列表   */  public List<String> splitBySize(String fileName, int byteSize)      throws IOException, InterruptedException {    List<String> parts = new ArrayList<String>();    File file = new File(fileName);    int count = (int) Math.ceil(file.length() / (double) byteSize);    int countLen = (count + "").length();    RandomAccessFile raf = new RandomAccessFile(fileName, "r");    long totalLen = raf.length();    CountDownLatch latch = new CountDownLatch(count);     for (int i = 0; i < count; i++) {      String partFileName = file.getPath() + "."          + leftPad((i + 1) + "", countLen, '0') + ".cvs";      int readSize=byteSize;      long startPos=(long)i * byteSize;      long nextPos=(long)(i+1) * byteSize;      if(nextPos>totalLen){        readSize= (int) (totalLen-startPos);      }      new SplitRunnable(readSize, startPos, partFileName, file, latch).run();      parts.add(partFileName);    }    latch.await();//等待所有文件寫完    //由于切割時可能會導致行被切斷，加工所有的的分割文件,合并行    mergeRow(parts);    return parts;  }   /**   * 分割處理Runnable   *   * @author supeidong   */  private class SplitRunnable implements Runnable {    int byteSize;    String partFileName;    File originFile;    long startPos;    CountDownLatch latch;    public SplitRunnable(int byteSize, long startPos, String partFileName,               File originFile, CountDownLatch latch) {      this.startPos = startPos;      this.byteSize = byteSize;      this.partFileName = partFileName;      this.originFile = originFile;      this.latch = latch;    }     public void run() {      RandomAccessFile rFile;      OutputStream os;      try {        rFile = new RandomAccessFile(originFile, "r");        byte[] b = new byte[byteSize];        rFile.seek(startPos);// 移動指針到每“段”開頭        int s = rFile.read(b);        os = new FileOutputStream(partFileName);        os.write(b, 0, s);        os.flush();        os.close();        latch.countDown();      } catch (IOException e) {        log.error(e.getMessage());        latch.countDown();      }    }  }   /**   * 合并被切斷的行   *   * @param parts   */  private void mergeRow(List<String> parts) {    List<PartFile> partFiles = new ArrayList<PartFile>();    try {      //組裝被切分表對象      for (int i=0;i<parts.size();i++) {        String partFileName=parts.get(i);        File splitFileTemp = new File(partFileName);        if (splitFileTemp.exists()) {          PartFile partFile = new PartFile();          BufferedReader reader=new BufferedReader(new InputStreamReader(new FileInputStream(splitFileTemp),"gbk"));          String firstRow = reader.readLine();          String secondRow = reader.readLine();          String endRow = readLastLine(partFileName);          partFile.setPartFileName(partFileName);          partFile.setFirstRow(firstRow);          partFile.setEndRow(endRow);          if(i>=1){            String prePartFile=parts.get(i - 1);            String preEndRow = readLastLine(prePartFile);            partFile.setFirstIsFull(getCharCount(firstRow+preEndRow)>getCharCount(secondRow));          }           partFiles.add(partFile);          reader.close();        }      }      //進行需要合并的行的寫入      for (int i = 0; i < partFiles.size() - 1; i++) {        PartFile partFile = partFiles.get(i);        PartFile partFileNext = partFiles.get(i + 1);        StringBuilder sb = new StringBuilder();        if (partFileNext.getFirstIsFull()) {          sb.append("/r/n");          sb.append(partFileNext.getFirstRow());        } else {          sb.append(partFileNext.getFirstRow());        }        writeLastLine(partFile.getPartFileName(),sb.toString());      }    } catch (Exception e) {      log.error(e.getMessage());    }  }   /**   * 得到某個字符出現的次數   * @param s   * @return   */  private int getCharCount(String s) {    int count = 0;    for (int i = 0; i < s.length(); i++) {      if (s.charAt(i) == cvsSeparator) {        count++;      }    }    return count;  }   /**   * 采用BufferedInputStream方式讀取文件行數   *   * @param filename   * @return   */  public int getFileRow(String filename) throws IOException {    InputStream is = new BufferedInputStream(new FileInputStream(filename));    byte[] c = new byte[1024];    int count = 0;    int readChars = 0;    while ((readChars = is.read(c)) != -1) {      for (int i = 0; i < readChars; ++i) {        if (c[i] == '/n')          ++count;      }    }    is.close();    return count;  }   /**   * 讀取最后一行數據   * @param filename   * @return   * @throws IOException   */  private String readLastLine(String filename) throws IOException {    // 使用RandomAccessFile , 從后找最后一行數據    RandomAccessFile raf = new RandomAccessFile(filename, "r");    long len = raf.length();    String lastLine = "";    if(len!=0L) {      long pos = len - 1;      while (pos > 0) {        pos--;        raf.seek(pos);        if (raf.readByte() == '/n') {          lastLine = raf.readLine();          lastLine=new String(lastLine.getBytes("8859_1"), "gbk");          break;        }      }    }    raf.close();    return lastLine;  }  /**   * 修改最后一行數據   * @param fileName   * @param lastString   * @return   * @throws IOException   */  private void writeLastLine(String fileName,String lastString){    try {      // 打開一個隨機訪問文件流，按讀寫方式      RandomAccessFile randomFile = new RandomAccessFile(fileName, "rw");      // 文件長度，字節數      long fileLength = randomFile.length();      //將寫文件指針移到文件尾。      randomFile.seek(fileLength);      //此處必須加gbk，否則會出現寫入亂碼      randomFile.write(lastString.getBytes("gbk"));      randomFile.close();    } catch (IOException e) {      log.error(e.getMessage());    }  }  /**   * 左填充   *   * @param str   * @param length   * @param ch   * @return   */  public static String leftPad(String str, int length, char ch) {    if (str.length() >= length) {      return str;    }    char[] chs = new char[length];    Arrays.fill(chs, ch);    char[] src = str.toCharArray();    System.arraycopy(src, 0, chs, length - src.length, src.length);    return new String(chs);  }   /**   * 合并文件行內部類   */  class PartFile {    private String partFileName;    private String firstRow;    private String endRow;    private boolean firstIsFull;     public String getPartFileName() {      return partFileName;    }     public void setPartFileName(String partFileName) {      this.partFileName = partFileName;    }     public String getFirstRow() {      return firstRow;    }     public void setFirstRow(String firstRow) {      this.firstRow = firstRow;    }     public String getEndRow() {      return endRow;    }     public void setEndRow(String endRow) {      this.endRow = endRow;    }     public boolean getFirstIsFull() {      return firstIsFull;    }     public void setFirstIsFull(boolean firstIsFull) {      this.firstIsFull = firstIsFull;    }  } }