java实现加密- 替换加密解密算法

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;


public class demo {
    static char[] jiami(char[] str, int n)     //加密算法
    {
        int i, len;
        char[] miwen;

        len = str.length;
        if ((miwen = new char[len + 1]) == null)    //申请内存
        {
            System.out.print("申请内存失败!\n");
            System.exit(1);
        }
        for (i = 0; i < len; i++)                        //移位替换
        {
            miwen[i] = (char) (str[i] + n);
        }
        miwen[len] = '\0';
        return miwen;
    }

    static char[] jiemi(char[] str, int n)        //解密算法
    {
        int i, len;
        char[] mingwen;

        len = str.length;
        if ((mingwen = new char[len + 1]) == null)//申请内存
        {
            System.out.print("申请内存失败!\n");
            System.exit(1);
        }
        for (i = 0; i < len; i++)                        //移位替换
        {
            mingwen[i] = (char) (str[i] - n);
        }
        mingwen[len] = '\0';
        return mingwen;
    }

    public static void main(String[] args) throws IOException {
        int i, n;
        char[] srcstr = new char[100];
        char[] miwen;
        String go;

        System.out.print("替换加密解密算法演示！\n");

        do {
            System.out.print("\n请先输入替换加密解密算法中的密钥：");
            Scanner input = new Scanner(System.in);
            n = input.nextInt();                        //密钥
            System.out.print("请输入明文字符串：");

            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
            String str = bufferedReader.readLine();
            srcstr = str.toCharArray();                //明文字符串

            System.out.print("输入的明文为：");
            for (i = 0; i < srcstr.length; i++) {
                System.out.print(srcstr[i]);
            }

            miwen = jiami(srcstr, n);                //加密
            System.out.print("\n加密后的密文为：");
            for (i = 0; i < srcstr.length; i++) {
                System.out.print(miwen[i]);
            }
            miwen = jiemi(miwen, n);                //解密
            System.out.print("\n解密出的明文为：");
            for (i = 0; i < srcstr.length; i++) {
                System.out.print(miwen[i]);
            }

            System.out.print("\n继续执行(y/n)?");
            go = input.next();
        } while (go.equalsIgnoreCase("y"));
        System.out.println("演示结束！");
    }

}