import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.List;public class FileSplit {private String filePath;//文件路径private long blockSize;//每一块大小private int blockNum;//块个个数private List<String> blockName;//每一块名称private String [] name;public FileSplit(){this.blockName = new ArrayList<String>();}public FileSplit(String filePath){this(filePath,1024);//未知的尺寸则默认1024
    }public FileSplit(String filePath, long blockSize){this();this.filePath = filePath;this.blockSize = blockSize;init();}public String getFilePath() {return filePath;}public void setFilePath(String filePath) {this.filePath = filePath;}public long getBlockSize() {return blockSize;}public void setBlockSize(long blockSize) {this.blockSize = blockSize;}public int getBlockNum() {return blockNum;}public void setBlockNum(int blockNum) {this.blockNum = blockNum;}public List<String> getBlockName() {return blockName;}public void setBlockName(List<String> blockName) {this.blockName = blockName;}private void initBlockName(String destPath){name = new File(filePath).getName().split("\\.");for(int i = 0; i < blockNum; i++){blockName.add(i,destPath + "\\" + name[0] + "_" + i + "." +name[1]);}}public void init(){File src = new File(filePath);//路径名不存在，或该路径表示的文件不存,或是文件夹在则结束。if(filePath == null || !src.exists()||src.isDirectory()){return;}if(blockSize >= src.length())this.blockSize = src.length();this.blockNum = (int)Math.ceil(src.length()*1.0/blockSize);}//destPath分割文件存放目录public void split(String destPath){//分割函数initBlockName(destPath);//初始化分割后的文件名long start = 0;for(int i = 0; i < blockNum; i++){if(i == blockNum - 1)//计算最后一块大小blockSize = new File(filePath).length()%blockSize;split_m(i,start,blockSize);//参数含义：第i块，读取位置，读取内容大小start += blockSize;//更新起始位置//    System.out.println(start);
        }}//开始分割，每次分割一块private void split_m(int blockNum,long start,long blockSize){int len = 0;byte[] flush = new byte[1024];RandomAccessFile raf = null;//源文件BufferedOutputStream bos = null;//分割后文件try {bos = new BufferedOutputStream(new FileOutputStream(new File(blockName.get(blockNum))));raf = new RandomAccessFile(new File(filePath),"r");try {raf.seek(start);//确定读取位置while(-1 != (len = raf.read(flush))){//当前块分割完成或文件已读取完跳出循环。//System.out.printf("%d %d %d %s\n",start,blockSize,len,blockName.get(blockNum));if((blockSize - len) >=0){//当前块大小-写入字节数，判断剩余字节bos.write(flush,0,len);//如果块剩余大小大于读取字节数，则写入读取字节数blockSize -= len;}else{//如果小于，则写入当前块剩余字节数bos.write(flush, 0, (int)blockSize);break;//分块文件已写满，跳出当前循环
                    }}bos.flush();bos.close();raf.close();} catch (IOException e) {// TODO Auto-generated catch block
                e.printStackTrace();}} catch (FileNotFoundException e) {// TODO Auto-generated catch block
            e.printStackTrace();}}public void Merge(String mergePath){//合并文件夹路径int len;byte[] flush = new byte[1024];InputStream is = null;OutputStream bos = null;for(int i = 0; i < blockNum; i++){try {//每次将一个分割后的文件写入合并文件中。//写入方法为追加bos = new BufferedOutputStream(new FileOutputStream(new File(mergePath,"merge." + name[1]),true));is = new BufferedInputStream(new FileInputStream(new File(blockName.get(i))));while(-1 != (len = is.read(flush))){//直到被分割的单个小文件读取完is.read(flush);//将读取内容放入flushbos.write(flush,0,len);//将读取内容写入文件。
                }bos.flush();bos.close();is.close();//释放当前资源，下次读取下一个小文件。} catch (FileNotFoundException e) {// TODO Auto-generated catch block
                e.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch block
                e.printStackTrace();}}}
}

public class Main {public static void main(String[] args){FileSplit f = new FileSplit("F:\\依风\\Desktop\\temp.txt",500);//被分割文件，分割后的字节数f.split("F:\\依风\\Desktop");//分割后小文件的存放位置f.Merge("F:\\依风\\Desktop");//合并后大文件的存放位置}
}