Exercise12_20.java

package ch_12;

import java.io.*;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

/**
 * *12.20 (Remove package statement) Suppose you have Java source files under the
 * directories chapter1, chapter2, . . . , chapter34. Write a program to
 * remove the statement package chapteri; in the first line for each Java
 * source file under the directory chapteri. Suppose chapter1, chapter2,
 * . . . , chapter34 are under the root directory srcRootDirectory.
 * <p>
 * The root directory and chapteri directory may contain other folders and files. Use
 * the following command to run the program:
 * java Exercise12_20 srcRootDirectory
 */
public class Exercise12_20 {
    private final static String USAGE = "java Exercise12_20 srcRootDirectory";
    private static final String SUB_DIR_PATTERN = "chapter*";
    private static final String SRC_FILE_PATTERN = "*.java";
    private static final String RESOLVE_PACKAGE_PATH = "src\\ch_12\\exercise12_18\\";

    public static void main(String[] args) {
        if (args == null || args.length != 1) {
            System.out.println("Usage: " + USAGE);
            System.exit(1);
        }

        List<Path> parentFiles = new ArrayList<>();

        Path parentPath = Paths.get(RESOLVE_PACKAGE_PATH, args[0]);
        if (!parentPath.toFile().exists()) {
            System.out.println("Error: Please enter the full filepath to your srcRootDirectory. The current " +
                    "directory is " + new File("").getAbsolutePath());
            System.exit(2);
        } else {
            System.out.println("Path is resolved: " + parentPath.toAbsolutePath());
        }


        try (DirectoryStream<Path> parentDirStream = Files.newDirectoryStream(parentPath, SUB_DIR_PATTERN)) {
            for (Path subPath : parentDirStream) {
                parentFiles.add(subPath);
            }

        } catch (
                IOException dirIterException) {
            System.out.println("The srcRootDirectory is empty or cannot be read because of system security settings.");
//            dirIterException.printStackTrace();

        }

        for (Path subPath : parentFiles) {
            System.out.println("Handling package reference writing for: " + subPath);
            handleRemovePackageStatement(subPath);
        }

    }

    private static void handleRemovePackageStatement(Path path) {
        String pkg = path.getName(path.getNameCount() - 1).toString();
        System.out.println("Iterating current package: " + pkg);

        try (DirectoryStream<Path> subDirStream = Files.newDirectoryStream(path, SRC_FILE_PATTERN)) {
            for (Path targetFilePath : subDirStream) {
                File targetFile = targetFilePath.toFile();
                ArrayList<String> fileContents = new ArrayList<>();

                FileReader reader = new FileReader(targetFile);
                BufferedReader bufferedReader = new BufferedReader(reader);

                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    fileContents.add(line);
                }
                bufferedReader.close();

                String removeStatement = "package";
                PrintWriter fileWriter = new PrintWriter(targetFile);

                for (String singleLine : fileContents) {
                    if (singleLine.contains(removeStatement)) {
                        System.out.println("Removed: " + singleLine + " from " + targetFile.getName());
                        continue;
                    }
                    fileWriter.println(singleLine);
                }
                fileWriter.close();
            }
        } catch (IOException ex) {
            System.out.println("An error occurred while handling the source files in " + pkg);
        }

    }
}