java凯撒密码实现----完美版

代码：

package ning.hao;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

import java.util.Scanner;

public class Cryptology {

char ciphertext[];//密文

int key;

char plaintext[];//明文

StringBuffer plaintextStr;

StringBuffer ciphertextStr;

final int max=500;

Cryptology(){

key=0;

plaintextStr=new StringBuffer("");

ciphertextStr=new StringBuffer("");

}

int setKey(){

System.out.println("请输入一个Caesar密钥");

Scanner sc=new Scanner(System.in);

try{

key=sc.nextInt()%26;

}

catch(Exception e){

System.out.println("需要输入整数！");

}

return key;

}

void getPlaintext(){//获得明文

plaintext=new char[max];

for(int j=0;j

plaintext[j]='@';

}

int i=0;

char ch=' ';

BufferedReader bf=new BufferedReader(new InputStreamReader(System.in));

System.out.println("请输入明文");

try {

ch=(char) bf.read();//获得字符

while(ch!='\r'&&ch!='\n'){

if(ch>='a'&&ch<='z'||ch>='A'&&ch<='Z'||ch==' '||ch==','||ch=='.'||ch=='!'){

plaintext[i]=ch;

i++;

}

else{

System.out.println("输入不支持！！");

break;

}

try{

ch=(char) bf.read();

}

catch(IOException e1){

}

}

}

catch(IOException e){}

}

void encryption(){//加密

int temp=0;

ciphertext=new char[max];

for(int j=0;j

ciphertext[j]='@';

}

for(int i=0;i

if(plaintext[i]!='@'){

temp=plaintext[i]+key;

if(plaintext[i]==' '||plaintext[i]==','||plaintext[i]=='.'||plaintext[i]=='!'){

ciphertext[i]=(char) (plaintext[i]);

}

if(plaintext[i]>='a'&&plaintext[i]<='z'){

if(temp>122)

ciphertext[i]=(char) (97+temp-123);

else{

ciphertext[i]=(char)temp;

}

}

if(plaintext[i]>='A'&&plaintext[i]<='Z'){

if((plaintext[i]+key)>90)

ciphertext[i]=(char)(65+temp-91);

else{

ciphertext[i]=(char)temp;

}

}

ciphertextStr.append(ciphertext[i]);

}

else{

break;

}

}

}

void deciphering(){//解密

char c=' ';

int temp=0;

for(int i=0;i

temp=ciphertext[i]-key;

if(ciphertext[i]!='@'){

if(plaintext[i]==' '||plaintext[i]==','||plaintext[i]=='.'||plaintext[i]=='!'){ c=(char)(ciphertext[i]);

}

if(ciphertext[i]>=97&&ciphertext[i]<=122){

c=(char)(temp);

if(temp<97){

c=(char)(26+temp);

}

}

if(ciphertext[i]>=65&&ciphertext[i]<=90){

c=(char)(temp);

if(temp<65){

c=(char)(26+temp);

}

}

plaintextStr.append(c);

}