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Thread: Java Program String Arrays Problem

  1. #1
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    Default 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++;
    } 
    }
    }


  2. #2
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    Default Re: Java Program String Arrays Problem

    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

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    Default Re: Java Program String Arrays Problem

    @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

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