import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Scanner;

public class Main {
 public static void main(String[] args) throws FileNotFoundException, IOException {
  File sourceFile = new File("ping.mp3");
//  System.out.println(sourceFile.exists());
  Scanner scanner = new Scanner(System.in);
  int numberOfPieces = 1;  //默认文件切割的数量
  System.out.println("Enter:");  //提示输入
  numberOfPieces = scanner.nextInt();  //输入
  scanner.close();  //输入后就关闭 装完逼就跑一个道理
  long fileLength = sourceFile.length() / numberOfPieces;  //分一下每一个小文件的大小
  byte[] b = new byte[1024];  //这个不解释 如果看不懂 就去看IO流去吧
  RandomAccessFile raf1 = new RandomAccessFile(sourceFile, "r");  
  int len = -1;
  for(int i = 0; i < numberOfPieces; i++) {
   String name = sourceFile.getName() + "." + (i+1);
   File file = new File(name);
   file.createNewFile();
   RandomAccessFile raf2 = new RandomAccessFile(file, "rw");
   while((len = raf1.read(b)) != -1) {
    raf2.write(b, 0, len);  //我觉的这样写比raf2.write(b);高明一些
    if(raf2.length() > fileLength)  //如果太大了就不在这个子文件写了 换下一个
     break;
   }
   raf2.close();
  }
  raf1.close();
 }
}

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

//文件合并 ping.n
public class Main {
 public static void main(String[] args) throws FileNotFoundException, IOException {
  File[] files = new File[10];
  String name = "ping.";
  File file = new File("ping.mp3");
  file.createNewFile();
  RandomAccessFile in = new RandomAccessFile(file, "rw");
  in.setLength(0);
  in.seek(0);
  byte[] bytes = new byte[1024];
  int len = -1;
  for(int i = 0; i < files.length; i++) {
   files[i] = new File(name + (i + 1));
   //System.out.println(files[i].exists());
   RandomAccessFile out = new RandomAccessFile(files[i], "rw");
   while((len = out.read(bytes)) != -1) {
    in.write(bytes, 0, len);
   }
   out.close();
  }
  in.close();
 }
}