Java Letter changes arraylist to string without commas but including white spaces

Question

Trying to complete this challenge from coderbyte: "Using the Java language, have the function LetterChanges(str) take the str parameter being passed and modify it using the following algorithm. Replace every letter in the string with the letter following it in the alphabet (ie. c becomes d, z becomes a). Then capitalize every vowel in this new string (a, e, i, o, u) and finally return this modified string."

The problem that i am having is the replace is pulling on the white spaces between characters, but I need it to preserve white spaces between words. Is there a better solution to this?

import java.util.Arrays;
import java.util.Scanner;

public class nextLetter {
    public static String LetterChanges(String str) {
        String[] inputString = str.replaceAll("[^a-zA-Z ]", "").split("");
        String[] alph= "abcdefghijklmnopqrstuvwxyz".split("");
        String[] vowel ="aeiouy".split("");
        for(int i=0; i<inputString.length; i++){
            int index= Arrays.asList(alph).indexOf(inputString[i])+1;
            inputString[i]= alph[index];
            if(Arrays.asList(vowel).indexOf(inputString[i])>0){
                inputString[i]= inputString[i].toUpperCase();
            }
        }
        //System.out.println(Arrays.toString(inputString));
        return Arrays.toString(inputString)
                .replace(" ","")
                .replace(",", "")  //remove the commas
                .replace("[", "")  //remove the right bracket
                .replace("]", "")//remove the left bracket
                .replace(" ","")
                .trim();
    }
    public static void main(String[] args) {
     Scanner s = new Scanner(System.in);
     System.out.println("enter a sentence");
     System.out.print(LetterChanges(s.nextLine())); 
}
}

Also I would not mind any pointers on how to improve this!

When i enter "test sentence" the ouput is UftUatfOUfOdf, when it should still be 2 separate "words" — Megan Majewski, Jun 09 '16 at 20:09
You are removing all the white space. If you want to preserve it don't remove it. Anyway @Michael has a better approach. — markbernard, Jun 09 '16 at 20:12

score 2 · Answer 1 · edited Jun 20 '20 at 09:12

Note: I've changed the method name to something a bit more descriptive. The method assumes that you're only working with lowercase letters.

public static void main(String[] args){
    System.out.println(shiftLetters("abcdz")); //bcdea
}

public static String shiftLetters(String str){
    StringBuilder shiftedWord = new StringBuilder();

    for (int i = 0; i < str.length(); i++){
        char currentChar = str.charAt(i);
        if (currentChar != ' '){
            currentChar += 1;
            if (currentChar > 'z'){
                currentChar = 'a';
            }
        }
        shiftedWord.append(currentChar);
    }

    return shiftedWord.toString();
}

This is the general logic flow of this program: create a cumulative StringBuilder object that will eventually be the return value of the method. Loop through all characters in the string; if the character is a whitespace character, then simply don't bother with it and add it onto the StringBuilder as is. Else, add one to the current character. Note that chars are an integral(4.2.1) primitive type, so you may add ints to a char as such. If it's the special case that the new char is out of the normal a-z range, set it back to a.

Taking Use of Java 8's API

public static String functionalShiftLetters(String str){
    return str
        .chars()
        .map(c -> c != ' ' ? c + 1 : c)
        .map(c -> c > 'z'? 'a' : c)
        .collect(StringBuilder::new,
                   StringBuilder::appendCodePoint, StringBuilder::append)
        .toString();
}

score 1 · Accepted Answer · answered Jun 09 '16 at 20:21

This preserves all other characters and handles the vowels.

public static String LetterChanges(String str)
{
    str = str.toLowerCase();
    StringBuilder sb = new StringBuilder();

    for (int i = 0; i < str.length(); i++)
    {
        char c = str.charAt(i);

        if ('a' <= c && c <= 'z')
        {
            c = (c == 'z') ? 'a' : (char) (c + 1);

            if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u')
            {
                c = Character.toUpperCase(c);
            }
        }
        sb.append(c);
    }
    return sb.toString();
}

Input: abcdefghijklmnopqrstuvwxyz 1234567890

Output: bcdEfghIjklmnOpqrstUvwxyzA 1234567890

score 0 · Answer 3 · answered Jun 09 '16 at 21:47

If have fixed alphabeth and swapping algorithm you can use a static dictionary.

public static HashMap<String,String> dictionary = new HashMap<>();

    static{
        dictionary.put(" ", " ");
        dictionary.put("a", "b");
        dictionary.put("b", "c");
        dictionary.put("c", "d");
        dictionary.put("d", "E");
        .
        .
        dictionary.put("z", "A");
    }

    public static  String shiftLetters(String str){         
        StringBuffer response = new StringBuffer();

        for (int i = 0; i < str.length(); i++){
            response.append(dictionary.get(String.valueOf(str.charAt(i))));
        }

        return response.toString();
    }

Java Letter changes arraylist to string without commas but including white spaces

3 Answers3

Taking Use of Java 8's API