How to use replace() for the last occurrence?

Question

The method String#replaceFirst() is used to replace the first occurrence of a substring in a string, but how should I proceed if I want to do this with the last occurrence?

The doubt is as follows how I will make the condition to analyze the string and if you find word use the methods shown.

Here deletes last character typed.

    texto = txtTexto.getText().toString();
        int length = texto.length();  
         txtTexto.setText(texto.substring(0, length-1));

Here analyzes condition to erase an entire word.

if (texto.substring(length-3, length).equals("sin")){

    txtTexto.setText(replaceLast(texto, "sin", ""));   
    }
    else if if (texto.substring(length-4, length).equals("asin")){

    txtTexto.setText(replaceLast(texto, "asin", ""));
    }

This way it works in the sin, but when it falls into the other condition eliminates the sin and maintains the to on the screen, if you reverse the order the condition of the sin works the Asin so smaller characters, type 2 characters do not work.

Answer 1

There is a ready-made solution in that reply in the OS:

public static String replaceLast(string text, string source, string target) {
    StringBuilder b = new StringBuilder(text);
    b.replace(text.lastIndexOf(source), text.lastIndexOf(source) + source.length(), target);
    return b.toString();
}

In the same question has another answer that uses Regex and is even more suitable as the replaceFirst():

public static String replaceLast(String text, String regex, String replacement) {
    return text.replaceFirst("(?s)(.*)" + regex, "$1" + replacement);
}

I put in the Github for future reference.

Answer 2

Another alternative would be to use the method String#substring():

public static String replaceLast(String texto, String substituir, String substituto) {
    // Retorna o índice da última ocorrência de "substituir"
    int pos = texto.lastIndexOf(substituir); 
    // Se encontrar o índice
    if (pos > -1) { 
       // Retorna os caracteres antecedentes de "substituir"
       return texto.substring(0, pos) 
        + substituto
        // Retorna os caracteres posteriores a "substituir"
        + texto.substring(pos + substituir.length(), texto.length()); 
    } else 
       // Se a palavra especificada em "substituir" não for encontrada não altera nada
       return texto;
}

Example of use:

public static void main (String[] args) throws java.lang.Exception
{
    System.out.println(replaceLast("foobarfoobar", "foo", "")); // foobarbar
}

Response based in that OS response.

Answer 3

Even though I have two answers that "solve your problem", I will try to leave one to complement and solve your error once and for all.

String[] toRemove = {"sin", "asin", "whatever_you_want", "hi"};

for (String isRemovable : toRemove){
    if (textTexto.contains(isRemovable){
        txtTexto.setText(replaceLast(texto, isRemovable, ""));
        break;
    } else {
        // code
    }
}

With this, the code will check whether your EditText contains one of the words present in toRemove. If yes, the word will be removed.