package io;

import java.io.FileInputStream;

import java.io.IOException;

public class IOUtil {

/**

 * 读取指定文件内容，按照16进制输出到控制台，为什么要按十六进制？

 * 并且每输出10个byte换行

 * @throws IOException

 */

    public static void printHex(String filename) throws IOException{

        //把文件作为字节流进行读操作

        FileInputStream in = new FileInputStream(filename);//FileInputStream具体实现了在文件上读取数据

      int b;

      int i=1;

      while((b=in.read())!=-1)//b=in.read()这就是程序核心

      {

          System.out.println(Integer.toHexString(b)+"  ");//将整型b转换成16进制表示的字符串？输出

          if(i++%10==0)

          {

              System.out.println();//每隔十个字节换行

          }

      }

    in.close();

    }

}

    /**

     * Reads a byte of data from this input stream. This method blocks

     * if no input is yet available.

     *

     * @return     the next byte of data, or <code>-1</code> if the end of the

     *             file is reached.

     * @exception  IOException  if an I/O error occurs.

     */

    public int read() throws IOException {

        return read0();

    }

    private native int read0() throws IOException;