package org.jeason.test1;
import java.io.*;

public class testfunction {
  
  public static void main(String[] args){
      
        System.out.println("请输入一个字母...");
        try{
          System.out.println(new testfunction().charChangeFunction(System.in.read()));
        } catch (Exception ex){
          ex.printStackTrace();
        }
  }
  
  String charChangeFunction(int charInt) throws Exception{
    String result = "输入了非字母";
    char[] letterArr = new char[26];
    for (int i = 0; i < letterArr.length; i++)
      letterArr[i] =(char)(65 + i);//大写字符
      
    int postion  = this.charIndexInArray(charInt,letterArr);
    
    if (postion != -1){
      try {
        result = this.changeCharResult(charInt,postion,letterArr);
      } catch (Exception ex){
        throw new Exception(ex.getMessage());
      }
    }
    return result;
  }
  
  int charIndexInArray(int inputInt,char[] arrChar){
    int result = -1;
    if(arrChar != null){
      
      for(int i = 0;i < arrChar.length; i++){
        if (inputInt <= (int)('Z')){
          if (inputInt == (int)arrChar[i]){
            result = i;
            break;
          }
        } else {
          if (inputInt - 32 == (int)arrChar[i]){
            result = i;
            break;
          }
        }
      }
    }
    
    return result;
  }
  
  String changeCharResult(int inputInt,int postionInt,char[]arrChar)throws Exception{
    if(arrChar != null && inputInt > -1 && postionInt >-1){
      int count = arrChar.length;
      int curIndex = count - postionInt -1;
      char reChar = arrChar[curIndex];
      if (inputInt >= (int)('a'))
        reChar = (char)(((int)reChar) + 32);
      return  String.valueOf(reChar);
    } else
      throw new Exception("输入了非字母");
  }
}