Use regex to replace all occurrences with CASE_INSENSITIVE (regardless of uppercase and lowercase)

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Use regex to replace all occurrences with CASE_INSENSITIVE (regardless of uppercase and lowercase)

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#1 by (6 votes)

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I try to make a method that finds and replaces words using regular expressions. The point is that I must be able to find and replace the word regardless of whether it has uppercase letters or not. This is the code that I carry:

public String reemplazar(String cadena,JFrame frame){
    StringBuffer reemplazar = new StringBuffer();
    StringBuffer buscar = new StringBuffer();
    StringBuffer respuesta = new StringBuffer();

    DlgReemplazar dlgReemplazar = new DlgReemplazar(
        frame, true, buscar, reemplazar, constantesGUI.REEMPLAZAR, respuesta
    );
    dlgReemplazar.setVisible(true);

    Pattern pat = Pattern.compile(buscar.toString(), Pattern.CASE_INSENSITIVE);
    Matcher mat = pat.matcher(cadena);

    if (mat.find() == true) {
        cadena = cadena.replaceAll(
            String.valueOf(buscar), String.valueOf(reemplazar)
        );
    }else{
        JOptionPane.showMessageDialog(null, "No se encontro el texto");
    }      
    return cadena;
}

java regex

asked by user3912930 09.11.2016 в 02:51

source

1 answer

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score 6 · Accepted Answer

The first point to correct is that you have to escape the special characters that may be in the variable. For example, if the user enters [hola] , I understand that I should look for that literal text, and not just one of those 4 characters.

To obtain a literal pattern from a string, use Pattern.quote () .

String patronBuscado = Pattern.quote(buscar.toString());

You would not need to escape if you use the Pattern switch. LITERAL , although I personally prefer to do it without this modifier to make it clearer or allow only a part of the pattern to escape.

And the same applies for the replacement, where you should use Matcher.quoteReplacement () .

String patronReemplazo = Matcher.quoteReplacement(reemplazar.toString());

Now yes, let's go to the main thing. As you may have seen, String.replaceAll () does not accept modifiers such as Pattern.CASE_INSENSITIVE , nor% Pattern , only strings.

There are 3 ways to replace it regardless of uppercase and lowercase.

Passing the online switch as (?i) into the regular expression:

cadena = cadena.replaceAll( "(?i)" + patronBuscado, patronReemplazo);

Use Matcher.replaceAll () about a compiled regular expression:

Pattern pat = Pattern.compile(patronBuscado, Pattern.CASE_INSENSITIVE);
Matcher mat = pat.matcher(cadena);
cadena = mat.replaceAll(patronReemplazo);

Alternatively you can use the methods Matcher.appendReplacement () and Matcher.appendTail () to be replaced with a StringBuffer and have more control over each of the replacements. However, this is unnecessary if you simply want to replace all occurrences with the same value.

Lastly, it must be taken into account that Pattern.CASE_INSENSITIVE only works in the ASCII range. If you would also like to replace accents, you should add Pattern.UNICODE_CASE (or the online modifier (?iu) ):

Pattern pat = Pattern.compile(patronBuscado, Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE);

Code:

String cadena = "Respuesta de SO en inglés";

StringBuffer buscar = new StringBuffer("EN INGLÉS");
String patronBuscado = Pattern.quote(buscar.toString());

StringBuffer reemplazar = new StringBuffer("en español");
String patronReemplazo = Matcher.quoteReplacement(reemplazar.toString());

Pattern pat = Pattern.compile(patronBuscado, Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE);
Matcher mat = pat.matcher(cadena);

if (mat.find()) {
    cadena = mat.replaceAll(patronReemplazo);
    System.out.println("Resultado: " + cadena);
} else {
    System.out.println("No se encontro el texto");
}

Demo:

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