怎样 从“D:\test.txt”中读入所有字符，并将其内容从头到尾反过来输出在屏幕上啊啊啊，求大神指教

Question

import java.io.*;  public class E7_1{          public static void main(String args[ ]){       int b;       try {          FileInputStream fis=new FileInputStream("D:\\test.txt");             while ( (b= fis.read()) !=-1)              System.out.print((char)b);             fis.close();       }                   catch (Exception e) {             system.out.println("出错了，原因是：");             system.out.println (e.toString());                }         }  }