我想用另一个字母替换一个字母。 “n”及以下的每个字母都有效，但上半部分不会改变字母。 有人可以解决这个问题吗？

Question

import java.util.Scanner; //import

public class project2 {

public static void main(String[] args) {
    
   
    Scanner in = new Scanner(System.in); //setting scanner
    System.out.println("Please enter the text you wish to encode."); //question
    String place = in.nextLine();
    
    place = place.replace('a', 'z'); //Making what letters replace with what
    place = place.replace('b', 'y');
    place = place.replace('c', 'x');
    place = place.replace('d', 'w');
    place = place.replace('e', 'v');
    place = place.replace('f', 'u');
    place = place.replace('g', 't');
    place = place.replace('h', 's');
    place = place.replace('i', 'r');
    place = place.replace('j', 'q');
    place = place.replace('k', 'p');
    place = place.replace('l', 'o');
    place = place.replace('m', 'n');
    place = place.replace('n', 'm');
    place = place.replace('o', 'l');
    place = place.replace('p', 'k');
    place = place.replace('q', 'j');
    place = place.replace('r', 'i');
    place = place.replace('s', 'h');
    place = place.replace('t', 'g');
    place = place.replace('u', 'f');
    place = place.replace('v', 'e');
    place = place.replace('w', 'd');
    place = place.replace('x', 'c');
    place = place.replace('w', 'b');
    place = place.replace('z', 'a');
    
    System.out.println(place); //typing the encoded message
}

}

This is what I have so far, but only the bottom half is working, the rest isn't replacing.

Answer 1

So taking a look at this, I decided to send the following through your code.

"abcdefghijklmnopqrstuvwxyz" 

In response, I got

"aycdefghijklmmlkjihgfedcya".

Which is almost what I would expect. What I would expect is

"abcdefghijklmmlkjihgfedcba". 

This leads me to the first problem.

place = place.replace('w', 'b');

That 'w' should be a 'y'.

Now the second problem is the one you're more specifically asking about. Why does it mirror at m? Well, we are going through this string sequentially and updating it after each change. So when we get to m al has been changed to zn. So as we continue through your code we will be changing all of the characters that were once al back to al.

Instead, try this answer https://stackoverflow.com/a/45668235/12572585 I've tested it and it works fine.