FileUtil

Useful filesystem level utilities

I'd like to share this utility class with lot of useful filesystem level utility methods. It minimizes the effort of the developer to write code for java.io stuff. Just call the utility method in a try-catch-finally block and handle the eventual IOException to your taste.

/*
 * net/balusc/util/FileUtil.java
 * 
 * Copyright (C) 2007 BalusC
 * 
 * This program is free software; you can redistribute it and/or modify it under the terms of the
 * GNU General Public License as published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License along with this program; if
 * not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

package net.balusc.util;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.ByteArrayInputStream;
import java.io.CharArrayReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;

/**
 * Useful file system level utilities.
 * 
 * @author BalusC
 * @link http://balusc.blogspot.com/2007/09/FileUtil.html
 */
public final class FileUtil {

    // Init ---------------------------------------------------------------------------------------

    private static final String LINE_SEPARATOR = System.getProperty("line.separator");

    // Constructors -------------------------------------------------------------------------------

    private FileUtil() {
        // Utility class, hide constructor.
    }

    // Writers ------------------------------------------------------------------------------------

    /**
     * Write byte array to file. If file already exists, it will be overwritten.
     * @param file The file where the given byte array have to be written to.
     * @param bytes The byte array which have to be written to the given file.
     * @throws IOException If writing file fails.
     */
    public static void write(File file, byte[] bytes) throws IOException {
        write(file, new ByteArrayInputStream(bytes), false);
    }

    /**
     * Write byte array to file with option to append to file or not. If not, then any existing
     * file will be overwritten.
     * @param file The file where the given byte array have to be written to.
     * @param bytes The byte array which have to be written to the given file.
     * @param append Append to file?
     * @throws IOException If writing file fails.
     */
    public static void write(File file, byte[] bytes, boolean append) throws IOException {
        write(file, new ByteArrayInputStream(bytes), append);
    }

    /**
     * Write byte inputstream to file. If file already exists, it will be overwritten.It's highly
     * recommended to feed the inputstream as BufferedInputStream or ByteArrayInputStream as those
     * are been automatically buffered.
     * @param file The file where the given byte inputstream have to be written to.
     * @param input The byte inputstream which have to be written to the given file.
     * @throws IOException If writing file fails.
     */
    public static void write(File file, InputStream input) throws IOException {
        write(file, input, false);
    }

    /**
     * Write byte inputstream to file with option to append to file or not. If not, then any
     * existing file will be overwritten. It's highly recommended to feed the inputstream as
     * BufferedInputStream or ByteArrayInputStream as those are been automatically buffered.
     * @param file The file where the given byte inputstream have to be written to.
     * @param input The byte inputstream which have to be written to the given file.
     * @param append Append to file?
     * @throws IOException If writing file fails.
     */
    public static void write(File file, InputStream input, boolean append) throws IOException {
        mkdirs(file);
        BufferedOutputStream output = null;

        try {
            int contentLength = input.available();
            output = new BufferedOutputStream(new FileOutputStream(file, append));
            while (contentLength-- > 0) {
                output.write(input.read());
            }
        } finally {
            close(input, file);
            close(output, file);
        }
    }

    /**
     * Write character array to file. If file already exists, it will be overwritten.
     * @param file The file where the given character array have to be written to.
     * @param chars The character array which have to be written to the given file.
     * @throws IOException If writing file fails.
     */
    public static void write(File file, char[] chars) throws IOException {
        write(file, new CharArrayReader(chars), false);
    }

    /**
     * Write character array to file with option to append to file or not. If not, then any
     * existing file will be overwritten.
     * @param file The file where the given character array have to be written to.
     * @param chars The character array which have to be written to the given file.
     * @param append Append to file?
     * @throws IOException If writing file fails.
     */
    public static void write(File file, char[] chars, boolean append) throws IOException {
        write(file, new CharArrayReader(chars), append);
    }

    /**
     * Write string value to file. If file already exists, it will be overwritten.
     * @param file The file where the given string value have to be written to.
     * @param string The string value which have to be written to the given file.
     * @throws IOException If writing file fails.
     */
    public static void write(File file, String string) throws IOException {
        write(file, new CharArrayReader(string.toCharArray()), false);
    }

    /**
     * Write string value to file with option to append to file or not. If not, then any existing
     * file will be overwritten.
     * @param file The file where the given string value have to be written to.
     * @param string The string value which have to be written to the given file.
     * @param append Append to file?
     * @throws IOException If writing file fails.
     */
    public static void write(File file, String string, boolean append) throws IOException {
        write(file, new CharArrayReader(string.toCharArray()), append);
    }

    /**
     * Write character reader to file. If file already exists, it will be overwritten. It's highly
     * recommended to feed the reader as BufferedReader or CharArrayReader as those are been
     * automatically buffered.
     * @param file The file where the given character reader have to be written to.
     * @param reader The character reader which have to be written to the given file.
     * @throws IOException If writing file fails.
     */
    public static void write(File file, Reader reader) throws IOException {
        write(file, reader, false);
    }

    /**
     * Write character reader to file with option to append to file or not. If not, then any
     * existing file will be overwritten. It's highly recommended to feed the reader as
     * BufferedReader or CharArrayReader as those are been automatically buffered.
     * @param file The file where the given character reader have to be written to.
     * @param reader The character reader which have to be written to the given file.
     * @param append Append to file?
     * @throws IOException If writing file fails.
     */
    public static void write(File file, Reader reader, boolean append) throws IOException {
        mkdirs(file);
        BufferedWriter writer = null;

        try {
            writer = new BufferedWriter(new FileWriter(file, append));
            int i = -1;
            while ((i = reader.read()) != -1) {
                writer.write(i);
            }
        } finally {
            close(reader, file);
            close(writer, file);
        }
    }

    /**
     * Write list of String records to file. If file already exists, it will be overwritten.
     * @param file The file where the given character reader have to be written to.
     * @param records The list of String records which have to be written to the given file.
     * @throws IOException If writing file fails.
     */
    public static void write(File file, List<String> records) throws IOException {
        write(file, records, false);
    }

    /**
     * Write list of String records to file with option to append to file or not. If not, then any
     * existing file will be overwritten.
     * @param file The file where the given character reader have to be written to.
     * @param records The list of String records which have to be written to the given file.
     * @param append Append to file?
     * @throws IOException If writing file fails.
     */
    public static void write(File file, List<String> records, boolean append) throws IOException {
        mkdirs(file);
        BufferedWriter writer = null;

        try {
            writer = new BufferedWriter(new FileWriter(file, append));
            for (String record : records) {
                writer.write(record);
                writer.write(LINE_SEPARATOR);
            }
        } finally {
            close(writer, file);
        }
    }

    // Readers ------------------------------------------------------------------------------------

    /**
     * Read byte array from file. Take care with big files, this would be memory hogging, rather
     * use readStream() instead.
     * @param file The file to read the byte array from.
     * @return The byte array with the file contents.
     * @throws IOException If reading file fails.
     */
    public static byte[] readBytes(File file) throws IOException {
        BufferedInputStream stream = (BufferedInputStream) readStream(file);
        byte[] bytes = new byte[stream.available()];
        stream.read(bytes);
        return bytes;
    }

    /**
     * Read byte stream from file.
     * @param file The file to read the byte stream from.
     * @return The byte stream with the file contents (actually: BufferedInputStream).
     * @throws IOException If reading file fails.
     */
    public static InputStream readStream(File file) throws IOException {
        return new BufferedInputStream(new FileInputStream(file));
    }

    /**
     * Read character array from file. Take care with big files, this would be memory hogging,
     * rather use readReader() instead.
     * @param file The file to read the character array from.
     * @return The character array with the file contents.
     * @throws IOException If reading file fails.
     */
    public static char[] readChars(File file) throws IOException {
        BufferedReader reader = (BufferedReader) readReader(file);
        char[] chars = new char[(int) file.length()];
        reader.read(chars);
        return chars;
    }

    /**
     * Read string value from file. Take care with big files, this would be memory hogging, rather
     * use readReader() instead.
     * @param file The file to read the string value from.
     * @return The string value with the file contents.
     * @throws IOException If reading file fails.
     */
    public static String readString(File file) throws IOException {
        return new String(readChars(file));
    }

    /**
     * Read character reader from file.
     * @param file The file to read the character reader from.
     * @return The character reader with the file contents (actually: BufferedReader).
     * @throws IOException If reading file fails.
     */
    public static Reader readReader(File file) throws IOException {
        return new BufferedReader(new FileReader(file));
    }

    /**
     * Read list of String records from file.
     * @param file The file to read the character writer from.
     * @return A list of String records which represents lines of the file contents.
     * @throws IOException If reading file fails.
     */
    public static List<String> readRecords(File file) throws IOException {
        BufferedReader reader = (BufferedReader) readReader(file);
        List<String> records = new ArrayList<String>();
        String record = null;

        try {
            while ((record = reader.readLine()) != null) {
                records.add(record);
            }
        } finally {
            close(reader, file);
        }

        return records;
    }

    // Copiers ------------------------------------------------------------------------------------

    /**
     * Copy file. Any existing file at the destination will be overwritten.
     * @param source The file to read the contents from.
     * @param destination The file to write the contents to.
     * @throws IOException If copying file fails.
     */
    public static void copy(File source, File destination) throws IOException {
        copy(source, destination, true);
    }

    /**
     * Copy file with the option to overwrite any existing file at the destination.
     * @param source The file to read the contents from.
     * @param destination The file to write the contents to.
     * @param overwrite Set whether to overwrite any existing file at the destination.
     * @throws IOException If the destination file already exists while <tt>overwrite</tt> is set
     * to false, or if copying file fails.
     */
    public static void copy(File source, File destination, boolean overwrite) throws IOException {
        if (destination.exists() && !overwrite) {
            throw new IOException(
                "Copying file " + source.getPath() + " to " + destination.getPath() + " failed."
                    + " The destination file already exists.");
        }

        mkdirs(destination);
        BufferedInputStream input = null;
        BufferedOutputStream output = null;

        try {
            input = new BufferedInputStream(new FileInputStream(source));
            output = new BufferedOutputStream(new FileOutputStream(destination));
            int contentLength = input.available();
            while (contentLength-- > 0) {
                output.write(input.read());
            }
        } finally {
            close(input, source);
            close(output, destination);
        }
    }

    // Movers -------------------------------------------------------------------------------------

    /**
     * Move (rename) file. Any existing file at the destination will be overwritten.
     * @param source The file to be moved.
     * @param destination The new destination of the file.
     * @throws IOException If moving file fails.
     */
    public static void move(File source, File destination) throws IOException {
        move(source, destination, true);
    }

    /**
     * Move (rename) file with the option to overwrite any existing file at the destination.
     * @param source The file to be moved.
     * @param destination The new destination of the file.
     * @param overwrite Set whether to overwrite any existing file at the destination.
     * @throws IOException If the destination file already exists while <tt>overwrite</tt> is set
     * to false, or if moving file fails.
     */
    public static void move(File source, File destination, boolean overwrite) throws IOException {
        if (destination.exists()) {
            if (overwrite) {
                destination.delete();
            } else {
                throw new IOException(
                    "Moving file " + source.getPath() + " to " + destination.getPath() + " failed."
                        + " The destination file already exists.");
            }
        }

        mkdirs(destination);

        if (!source.renameTo(destination)) {
            throw new IOException(
                "Moving file " + source.getPath() + " to " + destination.getPath() + " failed.");
        }
    }

    // Filenames ----------------------------------------------------------------------------------

    /**
     * Trim the eventual file path from the given file name. Anything before the last occurred "/"
     * and "\" will be trimmed, including the slash.
     * @param fileName The file name to trim the file path from.
     * @return The file name with the file path trimmed.
     */
    public static String trimFilePath(String fileName) {
        return fileName
            .substring(fileName.lastIndexOf("/") + 1)
            .substring(fileName.lastIndexOf("\\") + 1);
    }

    /**
     * Generate unique file based on the given path and name. If the file exists, then it will
     * add "[i]" to the file name as long as the file exists. The value of i can be between
     * 0 and 2147483647 (the value of Integer.MAX_VALUE).
     * @param filePath The path of the unique file.
     * @param fileName The name of the unique file.
     * @return The unique file.
     * @throws IOException If unique file cannot be generated, this can be caused if all file
     * names are already in use. You may consider another filename instead.
     */
    public static File uniqueFile(File filePath, String fileName) throws IOException {
        File file = new File(filePath, fileName);
        
        if (file.exists()) {

            // Split filename and add braces, e.g. "name.ext" --> "name[", "].ext".
            String prefix;
            String suffix;
            int dotIndex = fileName.lastIndexOf(".");

            if (dotIndex > -1) {
                prefix = fileName.substring(0, dotIndex) + "[";
                suffix = "]" + fileName.substring(dotIndex);
            } else {
                prefix = fileName + "[";
                suffix = "]";
            }

            int count = 0;

            // Add counter to filename as long as file exists.
            while (file.exists()) {
                if (count < 0) { // int++ restarts at -2147483648 after 2147483647.
                    throw new IOException("No unique filename available for " + fileName 
                        + " in path " + filePath.getPath() + ".");
                }

                // Glue counter between prefix and suffix, e.g. "name[" + count + "].ext".
                file = new File(filePath, prefix + (count++) + suffix);
            }
        }

        return file;
    }

    // Helpers ------------------------------------------------------------------------------------

    /**
     * Check and create missing parent directories for the given file.
     * @param file The file to check and create the missing parent directories for.
     * @throws IOException If creating parent directories fails.
     */
    private static void mkdirs(File file) throws IOException {
        checkFile(file);
        File parentFile = file.getParentFile();
        if (!parentFile.exists() && !parentFile.mkdirs()) {
            throw new IOException("Creating directories " + parentFile.getPath() + " failed.");
        }
    }

    /**
     * Check if the given file is actually a file.
     * @param file The file object to be checked.
     * @throws IOException If the given file is actually not a file.
     */
    private static void checkFile(File file) throws IOException {
        if (file.exists() && !file.isFile()) {
            throw new IOException("File " + file.getPath() + " is actually not a file.");
        }
    }

    /**
     * Close the given inputstream of the given file.
     * @param input The inputstream to be closed.
     * @param file The inputstream's subject.
     */
    private static void close(InputStream input, File file) {
        if (input != null) {
            try {
                input.close();
            } catch (IOException e) {
                closingFailed(file, e);
            }
        }
    }
    
    /**
     * Close the given outputstream of the given file.
     * @param input The outputstream to be closed.
     * @param file The outputstream's subject.
     */
    private static void close(OutputStream output, File file) {
        if (output != null) {
            try {
                output.close();
            } catch (IOException e) {
                closingFailed(file, e);
            }
        }
    }
    
    /**
     * Close the given reader of the given file.
     * @param input The reader to be closed.
     * @param file The reader's subject.
     */
    private static void close(Reader reader, File file) {
        if (reader != null) {
            try {
                reader.close();
            } catch (IOException e) {
                closingFailed(file, e);
            }
        }
    }
    
    /**
     * Close the given writer of the given file.
     * @param input The writer to be closed.
     * @param file The writer's subject.
     */
    private static void close(Writer writer, File file) {
        if (writer != null) {
            try {
                writer.close();
            } catch (IOException e) {
                closingFailed(file, e);
            }
        }
    }
    
    /**
     * Handle error when closing file failed.
     * @param file The file which isn't been closed.
     * @param ioException The IOException being thrown.
     */
    private static void closingFailed(File file, IOException e) {
        String message = "Closing file " + file.getPath() + " failed.";
        // Do your thing with the exception and the message. Print it, log it or mail it.
        System.err.println(message);
        e.printStackTrace();
    }

}

Copyright - GNU General Public License

(C) September 2007, BalusC