java (Replace words) Suppose you have a lot of files in a directory that contain words Exercisei_j, where i and j are digits. Write a program that pads a 0 before i if i is a single digit and 0 before j if j is a single digit. For example, the word Exercise2_1 in a file will be replaced by Exercise02_01. In Java, when you pass the symbol * from the command line, it refers to all files in the directory (see Supplement III.V). Use the following command to run your program: java Exercise12_27 *

Here's an example Java program that renames files in the directory according to the specified format:

import java.io.File;

public class Exercise12_27 {
    public static void main(String[] args) {
        String[] files = args.length > 0 ? args : new String[]{"*"};
        for (String filename : files) {
            File file = new File(filename);
            if (file.exists() && file.isFile()) {
                String newName = replaceDigits(filename);
                File newFile = new File(newName);
                if (newFile.exists()) {
                    System.out.println("File " + newName + " already exists!");
                } else {
                    if (file.renameTo(newFile)) {
                        System.out.println("File " + filename + " renamed to " + newName);
                    } else {
                        System.out.println("Failed to rename file " + filename);
                    }
                }
            }
        }
    }

    private static String replaceDigits(String filename) {
        String[] parts = filename.split("(?<=Exercise|Task)(\\d+)_(\\d+)(?=\\.)");
        if (parts.length == 3) {
            String i = parts[1];
            String j = parts[2];
            if (i.length() == 1) {
                i = "0" + i;
            }
            if (j.length() == 1) {
                j = "0" + j;
            }
            return parts[0] + i + "_" + j + "." + parts[3];
        } else {
            return filename;
        }
    }
}

You can run this program from the command line using the following command:

java Exercise12_27 *

This will rename all files in the current directory that match the pattern "Exercisei_j" or "Taski_j" to the format "Exerciseii_jj" or "Taskii_jj", respectively.