java实现加密-换位加密解密算法

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

public class demo {
    static char[] jiami(char[] str, int n) //加密算法
    {
        int i, j, k, d;
        int len;
        char[] temp, miwen, mtemp = {};

        len = str.length; //字符串长度
        if ((d = len % n) != 0) {
            len = len + n - d;
        }

        if ((temp = new char[len + 1]) == null) //申请内存
        {
            System.out.print("申请内存失败!\n");
            System.exit(1);
        }

        if ((miwen = new char[len + 1]) == null) //申请内存
        {
            System.out.print("申请内存失败!\n");
            System.exit(1);
        } else {
            mtemp = miwen;
        }

        System.arraycopy(str, 0, temp, 0, str.length);
        for (i = str.length; i < len; i++) {
            temp[i] = 32;
        }
        temp[len] = '\0';
        i = 0;
        for (k = 0; k < n; k++) //转换，加密
        {
            for (j = 0; j < len / n; j++) {
                mtemp[i] = temp[k + j * n];
                i++;
            }
        }
        mtemp[i] = '\0';
        temp = null;

        return miwen; //返回密文
    }

    static char[] jiemi(char[] str, int n) //解密算法
    {
        int i, j, k = 0, d;
        int len;
        char[] temp, mingwen, mtemp = {};

        len = str.length;

        if ((d = len % n) != 0) {
            len = len - d;
        }
        n = len / n;
        if ((temp = new char[len + 1]) == null) //申请内存
        {
            System.out.print("申请内存失败!\n");
            System.exit(1);
        }

        if ((mingwen = new char[len + 1]) == null) //申请内存
        {
            System.out.print("申请内存失败!\n");
            System.exit(1);
        } else {
            mtemp = mingwen;
        }

        System.arraycopy(str, 0, temp, 0, str.length);
        for (i = str.length; i < len; i++) {
            temp[i] = 32;
        }
        temp[len] = '\0';
        i = 0;
        for (k = 0; k < n; k++) //恢复出明文
        {
            for (j = 0; j < len / n; j++) {
                mtemp[i] = temp[k + j * n];
                i++;
            }
        }

        while (mtemp[--i] == 32) ;
        i++;
        mtemp[i] = '\0';
        return mingwen; //返回明文
    }


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

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

        do {
            System.out.print("\n请先输入换位加密矩阵每行的字符数：");
            Scanner input = new Scanner(System.in);
            n = input.nextInt(); //输入换位加密矩阵每行的字符数

            System.out.println("请输入明文：");
//输入明文字符串
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
            String str = bufferedReader.readLine();
            srcstr = str.toCharArray();

            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！");
    }
}