IO工具包commons-io

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.4</version>
</dependency>

FileUtils

/**

 * <li>writing to a file
 * <li>reading from a file
 * <li>make a directory including parent directories
 * <li>copying files and directories
 * <li>deleting files and directories
 * <li>converting to and from a URL
 * <li>listing files and directories by filter and extension
 * <li>comparing file content
 * <li>file last changed date
 * <li>calculating a checksum
 *
 * @version $Id: FileUtils.java 1349509 2012-06-12 20:39:23Z ggregory $
 */
public class FileUtils {

    /**
     * Instances should NOT be constructed in standard programming.
     */
    public FileUtils() {
        super();
    }

    /**
     * 獲取以directory/name[0]/name[1]/...爲路徑的文件實例
     */
    public static File getFile(File directory, String... names) {
        if (directory == null) {
            throw new NullPointerException("directorydirectory must not be null");
        }
        if (names == null) {
            throw new NullPointerException("names must not be null");
        }
        File file = directory;
        for (String name : names) {
            file = new File(file, name);
        }
        return file;
    }

    /**
     * 獲取以name[0]/name[1]/...爲相對路徑的文件實例
     */
    public static File getFile(String... names) {
        if (names == null) {
            throw new NullPointerException("names must not be null");
        }
        File file = null;
        for (String name : names) {
            if (file == null) {
                file = new File(name);
            } else {
                file = new File(file, name);
            }
        }
        return file;
    }

    /**
     * 獲取系統的臨時路徑
     */
    public static String getTempDirectoryPath() {
        return System.getProperty("java.io.tmpdir");
    }
    
    public static File getTempDirectory() {
        return new File(getTempDirectoryPath());
    }
    
    /**
     * 獲取用戶的home目錄
     */
    public static String getUserDirectoryPath() {
        return System.getProperty("user.home");
    }
    
    public static File getUserDirectory() {
        return new File(getUserDirectoryPath());
    }
    
    /**
     * 獲取文件讀取流,默認直接覆蓋文件內容
     */
    public static FileInputStream openInputStream(File file) throws IOException {
        if (file.exists()) {
            if (file.isDirectory()) {
                throw new IOException("File '" + file + "' exists but is a directory");
            }
            if (file.canRead() == false) {
                throw new IOException("File '" + file + "' cannot be read");
            }
        } else {
            throw new FileNotFoundException("File '" + file + "' does not exist");
        }
        return new FileInputStream(file);
    }

    public static FileOutputStream openOutputStream(File file) throws IOException {
        return openOutputStream(file, false);
    }

    /**
     * 獲取文件讀取流，並制定流是否可在原始文件上追加
     */
    public static FileOutputStream openOutputStream(File file, boolean append) throws IOException {
        if (file.exists()) {
            if (file.isDirectory()) {
                throw new IOException("File '" + file + "' exists but is a directory");
            }
            if (file.canWrite() == false) {
                throw new IOException("File '" + file + "' cannot be written to");
            }
        } else {
            File parent = file.getParentFile();
            if (parent != null) {
                if (!parent.mkdirs() && !parent.isDirectory()) {
                    throw new IOException("Directory '" + parent + "' could not be created");
                }
            }
        }
        return new FileOutputStream(file, append);
    }

    /**
     * 將字節量轉換爲可讀的容量
     */
    public static String byteCountToDisplaySize(BigInteger size) {
        String displaySize;

        if (size.divide(ONE_EB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_EB_BI)) + " EB";
        } else if (size.divide(ONE_PB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_PB_BI)) + " PB";
        } else if (size.divide(ONE_TB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_TB_BI)) + " TB";
        } else if (size.divide(ONE_GB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_GB_BI)) + " GB";
        } else if (size.divide(ONE_MB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_MB_BI)) + " MB";
        } else if (size.divide(ONE_KB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_KB_BI)) + " KB";
        } else {
            displaySize = String.valueOf(size) + " bytes";
        }
        return displaySize;
    }

    public static String byteCountToDisplaySize(long size) {
        return byteCountToDisplaySize(BigInteger.valueOf(size));
    }

    /**
     * 創建空文件
     */
    public static void touch(File file) throws IOException {
        if (!file.exists()) {
            OutputStream out = openOutputStream(file);
            IOUtils.closeQuietly(out);
        }
        boolean success = file.setLastModified(System.currentTimeMillis());
        if (!success) {
            throw new IOException("Unable to set the last modification time for " + file);
        }
    }

    public static File[] convertFileCollectionToFileArray(Collection<File> files) {
         return files.toArray(new File[files.size()]);
    }

    private static void innerListFiles(Collection<File> files, File directory,
            IOFileFilter filter, boolean includeSubDirectories) {
        File[] found = directory.listFiles((FileFilter) filter);
        
        if (found != null) {
            for (File file : found) {
                if (file.isDirectory()) {
                    if (includeSubDirectories) {
                        files.add(file);
                    }
                    innerListFiles(files, file, filter, includeSubDirectories);
                } else {
                    files.add(file);
                }
            }
        }
    }

    /**
     * 查詢目錄下的所有文件，並可用filter進行過濾
     */
    public static Collection<File> listFiles(
            File directory, IOFileFilter fileFilter, IOFileFilter dirFilter) {
        validateListFilesParameters(directory, fileFilter);

        IOFileFilter effFileFilter = setUpEffectiveFileFilter(fileFilter);
        IOFileFilter effDirFilter = setUpEffectiveDirFilter(dirFilter);

        //Find files
        Collection<File> files = new java.util.LinkedList<File>();
        innerListFiles(files, directory,
            FileFilterUtils.or(effFileFilter, effDirFilter), false);
        return files;
    }

    public static Collection<File> listFilesAndDirs(
            File directory, IOFileFilter fileFilter, IOFileFilter dirFilter) {
        validateListFilesParameters(directory, fileFilter);

        IOFileFilter effFileFilter = setUpEffectiveFileFilter(fileFilter);
        IOFileFilter effDirFilter = setUpEffectiveDirFilter(dirFilter);

        //Find files
        Collection<File> files = new java.util.LinkedList<File>();
        if (directory.isDirectory()) {
            files.add(directory);
        }
        innerListFiles(files, directory,
            FileFilterUtils.or(effFileFilter, effDirFilter), true);
        return files;
    }

    //... 對文件夾/文件的遍歷、複製、讀、寫、刪除等操作
}