In an encrypted message using Stack to invert each word of a String and using chatAt (int) to get characters specific to it, I had the following problem, when if you put a character on the stack, you can not use primitive types as a parameterized type.
How do I solve by creating a stack of type wrapper Character instead of declaring a stack of char implementing cryptography and message encryption?
As an example the text "An encrypted confidential message" should be "amu megasnem laicnedifnoc".
If you do not necessarily need to use stacks and use Java 8, everything can be done quite directly like this:
String texto = "Uma mensagem confidencial";
String reverso = Arrays.stream(texto.split("\s")) //quebra string por espaços
.map(s -> new StringBuilder(s).reverse().toString()) //inverte cada palavra
.collect(Collectors.joining(" ")); //junto tudo de novo
If you can not use Java 8, you can still do this:
String texto = "Uma mensagem confidencial";
String[] palavras = texto.split("\s");
StringBuilder sb = new StringBuilder();
for (String palavra : palavras) {
sb.append(new StringBuilder(palavra).reverse());
sb.append(" ");
}
String reverso = sb.toString();
If you prefer not to use the ready method of StringBuilder , you can retrieve the character vector of each word individually:
String texto = "Uma mensagem confidencial";
String[] palavras = texto.split("\s");
StringBuilder sb = new StringBuilder();
for (String palavra : palavras) {
char[] letras = palavra.toCharArray();
for (int i = letras.length - 1; i >= 0; i--) {
sb.append(letras[i]);
}
sb.append(" ");
}
String reverso = sb.toString();
Anyway, if you still prefer to use a stack for whatever reason, you can do this:
String texto = "Uma mensagem confidencial";
char[] letras = texto.toCharArray(); //vetor de caracteres
StringBuilder sb = new StringBuilder(letras.length); //buffer contendo resultado
Deque<Character> pilha = new ArrayDeque<>(letras.length); //pilha
for (char letra : letras) {
if (Character.isWhitespace(letra)) { //se for espaço
while (!pilha.isEmpty()) sb.append(pilha.pop()); //esvazia pilha
pilha.clear(); //limpa pilha
sb.append(letra); //mantém o espaço
} else {
pilha.push(letra);
}
}
while (!pilha.isEmpty()) sb.append(pilha.pop()); //esvazia resto da pilha
String reverso = sb.toString();