Thread: Java Program String Arrays Problem

The program allows the user to enter a phrase, and the program is supposed to print the phrase using ROT13 , which replaces each english letter with the letter 13 places forward, using arrays to store the characters. This is what I have so far but it doesn't work. When I run the code, after you enter a phrase, It will output letters starting with "O" and keep going (O P Q R...) for how many characters long the phrase was. Why is this happening?

import java.io.*;
 
public class program
{
 
public static void main (String [] args) throws IOException
{
BufferedReader myInput = new BufferedReader (new InputStreamReader (System.in));// Buffered Reader reads the number inputed 
 
 String key [] = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
    String keyA [] = {"N","O","P","Q","R","S","T","U","V","W","X","Y","Z","A","B","C","D","E","F","G","H","I","J","K","L","M"};
String letter;
 
System.out.println("Enter a phrase:");
String phrase = myInput.readLine();
int y = 0, i = 0;
while ( y <= phrase.length()){
 
letter = Character.toString(phrase.charAt(y));
 
while(i <= y){
 
if (letter != key[i]){
  keyA [i] = keyA[i];
}
i++;
}
System.out.println(keyA [i]);
y++;
} 
}
}

Honestly, it was too convoluted for me to figure out why it was doing what it was doing. Right off I saw you were trying to make while() loops do for() loop work. Also that assignment of keyA[i] to itself was pointless and when I removed that, it all became kind of pointless.

If you want to iterate through one thing relative to another, you need nested for() loops. For instance, if I have int arrays x and y, and I want to increment z every time x is equal to y (of course this is not runnable code):

int[] x = new int[10];
int[] y = new int[10];
int z;
 
for(int i = 0; i < x.length; i++) {
 
     for(int j = 0; j < y.length; j++) {
 
        if(x[i] == y[j]) {
           z++;
           break;
           }
         }
     }

i starts at 0, first index of x. j runs through the length of y until it finds that the digit being checked up on in the x array is equal to the target digit in the y array. Then it increments z and breaks. Back in the i-loop, i increments, and the process repeats, checking the next digit of x.

You are using while() loops trying to do this job. I suggest you get rid of them and replace with nested for()'s. They are much easier to understand, mostly because they are a standard.

-summit45

@incxx "It will output letters starting with "O" and keep going (O P Q R...) for how many characters long the phrase was. Why is this happening?" Step through the code to see what is happening. Sounds like there is a problem with the loops. Follow through and see why it does what it does

@summit45 Please read The problem with spoonfeeding