How to create a regex to filter and delete files with a particular chunk in the name

Question

I’m trying to figure out a way to delete files that windows duplicates when making multiple copies. I was able to do something by creating the code below:

import java.util.*;
import java.io.*;


public class FileCreator{

    public static void main(String[] args) throws Exception{

        File f = f = new File(".");
        File[] files = f.listFiles();

        for(File fl : files){
            String fileName = fl.getName();
            if(fileName.contains("Copia - Copia")){
                    System.out.println(fileName);
            }

        }
    }
}

I created some files, as follows the print below:

And the mourning was:

C:\Users\diego\Desktop\Nova pasta>java FileCreator
File 0 - Copia - Copia.txt
File 10 - Copia - Copia.txt
File 12 - Copia - Copia.txt
File 14 - Copia - Copia.txt
File 16 - Copia - Copia.txt
File 18 - Copia - Copia.txt
File 2 - Copia - Copia.txt
File 4 - Copia - Copia.txt
File 6 - Copia - Copia.txt
File 8 - Copia - Copia.txt

This form even suits me, because I just replace the text output of the condition within the loop by a simple fl.delete(); but would like to have more control over what is excluded, using a regex.

I started to do something according to below, but I could not create a regex that can detect the "Copia - Copia" exactly at the end of the file name, and then delete it.

    Pattern p = Pattern.compile("");
    Matcher m;

    f = new File(".");
    File[] files = f.listFiles();

    for(File fl : files){
        String fileName = fl.getName();
        m = p.matcher(fileName);
        if(m.find()){
            //fl.delete();
            System.out.println(fileName + " deletado");
        }
    }

How do I make a regex that fills these aquivos?

Note: detecting the extension is irrelevant, I just need to detect the Copia - Copia which is like windows renames duplicates of duplicates, adding at the end of the file name.

_{If possible, I would like to understand the functioning of the expression as well}

Answer 1

The regex can be like this Copia - Copia.[^.]+$

Explanation:

Copia - Copia\\.[^.]+$
^                ^   ^
1                2   3

1. The Copia - Copia\\. is the party you wish to find

2. [^.] the sign of ^ if you’re inside [...] indicates negation, that is any character within [^....] will be ignored in match, then after the points I used it so that anything can be the file extension, except another point.

3. The $ is what defines the file name (the String) should end exactly as it comes before, in case it should end with Copia - Copia.[qualquer extensão]

Alternatively you can use C[oó]pia - C[oó]pia\\.[^.]+$ there are situations with accents and without accents, note that it varies if it is Unicode

The use would look something like final Pattern regex = Pattern.compile("C[oó]pia - C[oó]pia\\.[^.]+$");

An example with List<String> to test:

import java.util.ArrayList;
import java.util.List;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

class Exemplo
{
    public static void main(String[] args)
    {
        final Pattern regex = Pattern.compile("Copia - Copia\\.[^.]+$");

        List<String> files = new ArrayList<String>();

        files.add("File 123 - Copia.txt");
        files.add("File 10 - Copia - Copia.java");
        files.add("File 12 - Copia.java");
        files.add("File 14 - Copia - Copia.txt");
        files.add("File 16 - Copia.txt");
        files.add("File 18 - Copia - Copia.log");
        files.add("File 2 - Copia.txt");
        files.add("File 4 - Copia.log");
        files.add("File 6 - Copia - Copia.txt");
        files.add("File 8 - Copia.txt");

        for (String file : files)
        {
            if (regex.matcher(file).find())
            {
                System.out.println("Encontrado: " + file);
            }
        }
    }
}

Example in http://ideone.com/Ph7CJC

---

It is also possible to use String.matches, but with it will need to add .* at the front, because for some reason he ignores it if it is not done, so .*Copia - Copia\\.[^.]+$. However, as @Victorstafusa said, maybe this might compromise performance a little, depending on how many times you will perform (I haven’t been able to confirm yet)

Explanation:

.*Copia - Copia\\.[^.]+$
^  ^               ^   ^
1  2               3   4

It would look something like:

for (String file : files)
{
    if (file.matches("Copia - Copia\\.[^.]+$"))
    {
        System.out.println("Encontrado: " + file);
    }
}

1. .* finds any (group of) characters(s) that come before the desired text

2. The Copia - Copia\\. is the party you wish to find

3. [^.] the sign of ^ if you’re inside [...] indicates negation, that is any character within [^....] will be ignored in match, so after the points I used it so that anything can be the file extension, except another point.

4. The $ is what defines the file name (the String) should end exactly as it comes before, in case it should end with [qualquer caractere]Copia - Copia.[qualquer extensão]

Alternatively you can use .*C[oó]pia - C[oó]pia\\.[^.]+$ there are situations with accents and without accents, note that it varies if it is Unicode

The use would look something like if (file.matches("C[oó]pia - C[oó]pia\\.[^.]+$")) {

Answer 2

You can use the following regular expression:

Pattern.compile("Copia - Copia\\.[a-zA-Z]{3,4}$");

Where:

• Copia - Copia is the text you are looking for;
• \\. is the literal character .. Normal would just be \ but how the expression is in a string we have to escape it once;
• [a-zA-Z] delimits that the character must be between a and z or A and Z;
• {3, 4} is related to the number of characters, which should be 3 or 4;
• $ means it’s at the end of string;

That is to say:

Search for the text Copia - Copia followed by a ., 3 or 4 letters of a to Z at the end of a string;

Answer 3

Use that expression:

(Copia - Copia)

Parentheses define a group of characters to be 'captured' from the string.

Sign in to this site http://regexr.com/3eoeg to see working.

Answer 4

String trechoParaRemover = "(Copia - Copia)";
fileName = filename.replace(trechoParaRemover,"");

Only this would solve your case, I do not believe you need a regular expression or delete().