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 *

Okay, here's a basic outline of the program:

1. Get the list of all files in the directory using the command line argument passed (*).
2. Loop through each file in the list.
3. Read the contents of the file.
4. Use regular expressions to find all occurrences of the pattern Exercisei_j in the file content.
5. For each occurrence, extract the values of i and j.
6. If i or j is a single digit, pad a 0 before it.
7. Replace the original occurrence of Exercisei_j with the new string Exerciseii_jj.
8. Write the modified content back to the file.

Here's a sample Java code that you can use as a starting point:

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

public class Exercise12_27 {
    public static void main(String[] args) {
        String searchPattern = "Exercise(\\d)_(\\d)";
        String replacePattern = "Exercise0$1_0$2";

        // Get the list of all files in the directory
        File dir = new File(".");
        File[] files = dir.listFiles();

        // Loop through each file in the list
        for (File file : files) {
            if (file.isFile()) {
                // Read the contents of the file
                String content = readFileContent(file);

                // Use regular expressions to find all occurrences of the pattern Exercisei_j in the file content
                Pattern pattern = Pattern.compile(searchPattern);
                Matcher matcher = pattern.matcher(content);

                // For each occurrence, extract the values of i and j
                while (matcher.find()) {
                    String i = matcher.group(1);
                    String j = matcher.group(2);

                    // If i or j is a single digit, pad a 0 before it
                    if (i.length() == 1) {
                        i = "0" + i;
                    }
                    if (j.length() == 1) {
                        j = "0" + j;
                    }

                    // Replace the original occurrence of Exercisei_j with the new string Exerciseii_jj
                    String replacement = "Exercise" + i + "_" + j;
                    content = content.replace(matcher.group(), replacement);
                }

                // Write the modified content back to the file
                writeFileContent(file, content);
            }
        }
    }

    private static String readFileContent(File file) {
        try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
            StringBuilder content = new StringBuilder();
            String line;
            while ((line = reader.readLine()) != null) {
                content.append(line).append("\n");
            }
            return content.toString();
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    private static void writeFileContent(File file, String content) {
        try (BufferedWriter writer = new BufferedWriter(new FileWriter(file))) {
            writer.write(content);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Note that this is just a basic implementation and you may need to modify it to suit your specific requirements.