How to decode a code that modifies vowels

Question

I am trying to create a code that modifies vowels. As an example of an input would be:

2n1v5rs0 5 t2d0 0 q25 5x1st5 f1s1c4m5nt5, 1ncl21nd0 t0d0s 0s ...

and the exit would be:

universe and everything that exists physically, including all ...

I thought I’d start the code with something like this:

Scanner reader = new Scanner(System.in);

if()
    char a = reader.next().charAt(4);
    char e = reader.next().charAt(5);
    char i = reader.next().charAt(1);
    char o = reader.next().charAt(0);
    char u = reader.next().charAt(2);
else 

But I don’t know what to put in if and else.

Answer 1

Use the method public String replace(char oldChar, char newChar)

import java.io.*;
public class Test {

 public static void main(String args[]) {
   String Str = new String("2n1v5rs0 5 t2d0 0 q25 5x1st5 f1s1c4m5nt5, 1ncl21nd0 t0d0s 0s");

   Str = Str.replace("1", "i");
   Str = Str.replace("2", "u");
   Str = Str.replace("0", "o");
   Str = Str.replace("4", "a");
   Str = Str.replace("5", "e");
   System.out.print(Str);
 }
}

Answer 2

An alternative is to create a Map that maps each character that will be replaced by its respective letter, and use a StringBuilder to make the replacements:

String texto = "2n1v5rs0 5 t2d0 0 q25 5x1st5 f1s1c4m5nt5, 1ncl21nd0 t0d0s 0s";

Map<Character, Character> trocas = new HashMap<Character, Character>();
trocas.put('4', 'a'); // troca o "4" por "a"
trocas.put('5', 'e'); // troca o "5" por "e"
trocas.put('1', 'i'); // e assim por diante
trocas.put('0', 'o');
trocas.put('2', 'u');

StringBuilder sb = new StringBuilder(texto);
for (int i = 0; i < sb.length(); i++) {
    char ch = sb.charAt(i);
    if (trocas.containsKey(ch)) {
        sb.setCharAt(i, trocas.get(ch));
    }
}
String novoTexto = sb.toString();

To another answer uses replace, which also works, but every call from replace creates a new String. Using an instance of StringBuilder, I do all the replacements on it and only at the end I Gero the new String.

---

Another alternative is to get the array of char's of String using toCharArray, make the replacements in this array and at the end use it to create the new String:

Map<Character, Character> trocas = etc... // igual ao código anterior
char[] charArray = texto.toCharArray();
for (int i = 0; i < charArray.length; i++) {
    char ch = charArray[i];
    if (trocas.containsKey(ch)) {
        charArray[i] = trocas.get(ch);
    }
}
String novoTexto = new String(charArray);

This alternative also avoids creating multiple strings, generating a new one only at the end.