簡單密碼學實作

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凱薩密碼

java

import java.util.*;
public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc=new Scanner(System.in);
		int move=sc.nextInt();
		String plaintext=sc.nextLine();
		String ciphertext= plaintext;
		char[] ciphertextChars = ciphertext.toCharArray();
		for(int i=0;i<plaintext.length();i++) {
			if(plaintext.charAt(i)==' ') 
				ciphertextChars[i] = ' ';							
			else if(plaintext.charAt(i)<'a') {
				ciphertextChars[i] = (char)(plaintext.charAt(i)+move);
				if((plaintext.charAt(i)+move)>'Z')
					ciphertextChars[i] = (char)(plaintext.charAt(i)+move-26);
			}
			else {
				ciphertextChars[i] = (char)(plaintext.charAt(i)+move);
				if((plaintext.charAt(i)+move)>'z')
					ciphertextChars[i] = (char)(plaintext.charAt(i)+move-26);
			}
					
		}
		ciphertext = String.valueOf(ciphertextChars);
		System.out.print(ciphertext);
		sc.close();
	}

}