Question

I want to make a program that takes a string and encrypts it.

During execution of program it is supposed to convert a string to char array. Then, a switch statement runs through the array to replace a with b and vice versa.

However, the programm just returns the same as at the start! here is the code

import java.lang.*;
import java.util.Scanner;


public class Program
{

    public static void main(String args[]) 
    {
        Scanner input = new Scanner(System.in);
        String pw = input.next();
        char pwa[] = pw.toCharArray();

        for(char c : pwa ){
          switch(c){
            case 'a':
            c = 'b';
            break;
            case 'b': 
            c ='a';
            break;
          }
        }
        String convpw = new String(pwa);
        System.out.println(convpw);
    }
}

Answer 1

You’re just changing the variable c, not pwa, and c is local to your loop.

You can do this :

for (int i=0; i<pwa.length; i++) {
    switch(pwa[i]){
    case 'a':
       pwa[i] = 'b';
       break;
    case 'b': 
       pwa[i] ='a';
       break;
    }
}