FileUtils.java

package me.shouheng.utils.store;

import android.content.ContentUris;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.os.Build.VERSION_CODES;
import android.os.Environment;
import android.provider.DocumentsContract;
import android.provider.MediaStore;
import android.provider.OpenableColumns;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RequiresApi;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileFilter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

import me.shouheng.utils.UtilsApp;
import me.shouheng.utils.data.StringUtils;

/**
 * 用来处理文件的拷贝、增加和删除等逻辑
 *
 * @author Shouheng Wang 2019-05-08 21:30
 */
public final class FileUtils {

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

    /*------------------------------------- 查询方法 ----------------------------------------*/

    public static boolean isStorageReadable() {
        String state = Environment.getExternalStorageState();
        return Environment.MEDIA_MOUNTED_READ_ONLY.equals(state);
    }

    public static boolean isStorageWritable() {
        String state = Environment.getExternalStorageState();
        return Environment.MEDIA_MOUNTED.equals(state);
    }

    @RequiresApi(api = VERSION_CODES.KITKAT)
    public static String getFilePath(@NonNull final Uri uri) {
        Context context = UtilsApp.getApp();
        if (DocumentsContract.isDocumentUri(context, uri)) {
            if (isExternalStorageDocument(uri)) {
                final String docId = DocumentsContract.getDocumentId(uri);
                final String[] split = docId.split(":");
                final String type = split[0];
                if ("primary".equalsIgnoreCase(type)) {
                    return Environment.getExternalStorageDirectory() + "/" + split[1];
                }
            } else if (isDownloadsDocument(uri)) {
                final Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"),
                        Long.parseLong(DocumentsContract.getDocumentId(uri)));
                return getDataColumn(context, contentUri, null, null);
            } else if (isMediaDocument(uri)) {
                final String docId = DocumentsContract.getDocumentId(uri);
                final String[] split = docId.split(":");
                final String type = split[0];
                Uri contentUri = createURI(type);
                final String selection = "_id=?";
                final String[] selectionArgs = new String[]{split[1]};
                return getDataColumn(context, contentUri, selection, selectionArgs);
            }
        } else if ("content".equalsIgnoreCase(uri.getScheme())) {
            return getDataColumn(context, uri, null, null);
        } else if ("file".equalsIgnoreCase(uri.getScheme())) {
            return uri.getPath();
        }
        return null;
    }

    public static File getFileByPath(final String filePath) {
        return StringUtils.isSpace(filePath) ? null : new File(filePath);
    }

    public static boolean isFileExists(final String filePath) {
        return isFileExists(getFileByPath(filePath));
    }

    public static boolean isFileExists(final File file) {
        return file != null && file.exists();
    }

    public static boolean isFile(final String filePath) {
        return isFile(getFileByPath(filePath));
    }

    public static boolean isFile(final File file) {
        return file != null && file.exists() && file.isFile();
    }

    public static boolean isDir(final String dirPath) {
        return isDir(getFileByPath(dirPath));
    }

    public static boolean isDir(final File file) {
        return file != null && file.exists() && file.isDirectory();
    }

    public static String getFileName(@NonNull final Uri uri) {
        String fileName = "";
        Cursor cursor = null;
        try {
            cursor = UtilsApp.getApp().getContentResolver().query(
                    uri, new String[]{OpenableColumns.DISPLAY_NAME}, null, null, null);
            if (cursor != null && cursor.moveToFirst()) {
                fileName = cursor.getString(cursor.getColumnIndex(OpenableColumns.DISPLAY_NAME));
            } else {
                fileName = uri.getLastPathSegment();
            }
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (cursor != null) {
                cursor.close();
            }
        }
        return fileName;
    }

    public static String getFileName(final File file) {
        if (file == null) return "";
        return getFileName(file.getAbsolutePath());
    }

    public static String getFileName(final String filePath) {
        if (StringUtils.isSpace(filePath)) return "";
        int lastSep = filePath.lastIndexOf(File.separator);
        return lastSep == -1 ? filePath : filePath.substring(lastSep + 1);
    }

    public static String getFileNameNoExtension(final File file) {
        if (file == null) return "";
        return getFileNameNoExtension(file.getPath());
    }

    public static String getFileNameNoExtension(final String filePath) {
        if (StringUtils.isSpace(filePath)) return "";
        int lastPoi = filePath.lastIndexOf('.');
        int lastSep = filePath.lastIndexOf(File.separator);
        if (lastSep == -1) {
            return (lastPoi == -1 ? filePath : filePath.substring(0, lastPoi));
        }
        if (lastPoi == -1 || lastSep > lastPoi) {
            return filePath.substring(lastSep + 1);
        }
        return filePath.substring(lastSep + 1, lastPoi);
    }

    public static String getFileExtension(final File file) {
        if (file == null) return "";
        return getFileExtension(file.getPath());
    }

    public static String getFileExtension(final String filePath) {
        if (StringUtils.isSpace(filePath)) return "";
        int lastPoi = filePath.lastIndexOf('.');
        int lastSep = filePath.lastIndexOf(File.separator);
        if (lastPoi == -1 || lastSep >= lastPoi) return "";
        return filePath.substring(lastPoi + 1);
    }

    public static String getDirName(final File file) {
        if (file == null) return "";
        return getDirName(file.getAbsolutePath());
    }

    public static String getDirName(final String filePath) {
        if (StringUtils.isSpace(filePath)) return "";
        int lastSep = filePath.lastIndexOf(File.separator);
        return lastSep == -1 ? "" : filePath.substring(0, lastSep + 1);
    }

    public static long getFileLastModified(final String filePath) {
        return getFileLastModified(getFileByPath(filePath));
    }

    public static long getFileLastModified(final File file) {
        if (file == null) return -1;
        return file.lastModified();
    }

    public static String getFileCharsetSimple(final String filePath) {
        return getFileCharsetSimple(getFileByPath(filePath));
    }

    public static String getFileCharsetSimple(final File file) {
        int p = 0;
        InputStream is = null;
        try {
            is = new BufferedInputStream(new FileInputStream(file));
            p = (is.read() << 8) + is.read();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (is != null) {
                    is.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        switch (p) {
            case 0xefbb:
                return "UTF-8";
            case 0xfffe:
                return "Unicode";
            case 0xfeff:
                return "UTF-16BE";
            default:
                return "GBK";
        }
    }

    public static int getFileLines(final String filePath) {
        return getFileLines(getFileByPath(filePath));
    }

    public static int getFileLines(final File file) {
        int count = 1;
        InputStream is = null;
        try {
            is = new BufferedInputStream(new FileInputStream(file));
            byte[] buffer = new byte[1024];
            int readChars;
            if (LINE_SEP.endsWith("\n")) {
                while ((readChars = is.read(buffer, 0, 1024)) != -1) {
                    for (int i = 0; i < readChars; ++i) {
                        if (buffer[i] == '\n') ++count;
                    }
                }
            } else {
                while ((readChars = is.read(buffer, 0, 1024)) != -1) {
                    for (int i = 0; i < readChars; ++i) {
                        if (buffer[i] == '\r') ++count;
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (is != null) {
                    is.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return count;
    }

    public static String getDirSize(final String dirPath) {
        return getDirSize(getFileByPath(dirPath));
    }

    public static String getDirSize(final File dir) {
        long len = getDirLength(dir);
        return len == -1 ? "" : byte2FitMemorySize(len);
    }

    public static String getFileSize(final String filePath) {
        long len = getFileLength(filePath);
        return len == -1 ? "" : byte2FitMemorySize(len);
    }

    public static String getFileSize(final File file) {
        long len = getFileLength(file);
        return len == -1 ? "" : byte2FitMemorySize(len);
    }

    public static long getDirLength(final String dirPath) {
        return getDirLength(getFileByPath(dirPath));
    }

    public static long getDirLength(final File dir) {
        if (!isDir(dir)) return -1;
        long len = 0;
        File[] files = dir.listFiles();
        if (files != null && files.length != 0) {
            for (File file : files) {
                if (file.isDirectory()) {
                    len += getDirLength(file);
                } else {
                    len += file.length();
                }
            }
        }
        return len;
    }

    public static long getFileLength(final String filePath) {
        boolean isURL = filePath.matches("[a-zA-z]+://[^\\s]*");
        if (isURL) {
            try {
                HttpURLConnection conn = (HttpURLConnection) new URL(filePath).openConnection();
                conn.setRequestProperty("Accept-Encoding", "identity");
                conn.connect();
                if (conn.getResponseCode() == 200) {
                    return conn.getContentLength();
                }
                return -1;
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return getFileLength(getFileByPath(filePath));
    }

    public static long getFileLength(final File file) {
        if (!isFile(file)) return -1;
        return file.length();
    }

    public static String getFileMD5ToString(final String filePath) {
        File file = StringUtils.isSpace(filePath) ? null : new File(filePath);
        return getFileMD5ToString(file);
    }

    public static String getFileMD5ToString(final File file) {
        return StringUtils.bytes2HexString(getFileMD5(file));
    }

    public static byte[] getFileMD5(final String filePath) {
        return getFileMD5(getFileByPath(filePath));
    }

    public static byte[] getFileMD5(final File file) {
        if (file == null) return null;
        DigestInputStream dis = null;
        try {
            FileInputStream fis = new FileInputStream(file);
            MessageDigest md = MessageDigest.getInstance("MD5");
            dis = new DigestInputStream(fis, md);
            byte[] buffer = new byte[1024 * 256];
            while (true) {
                if (!(dis.read(buffer) > 0)) break;
            }
            md = dis.getMessageDigest();
            return md.digest();
        } catch (NoSuchAlgorithmException | IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (dis != null) {
                    dis.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    public static List<File> listFilesInDir(final String dirPath) {
        return listFilesInDir(dirPath, false);
    }

    public static List<File> listFilesInDir(final File dir) {
        return listFilesInDir(dir, false);
    }

    public static List<File> listFilesInDir(final String dirPath, final boolean isRecursive) {
        return listFilesInDir(getFileByPath(dirPath), isRecursive);
    }

    public static List<File> listFilesInDir(final File dir, final boolean isRecursive) {
        return listFilesInDirWithFilter(dir, new FileFilter() {
            @Override
            public boolean accept(File pathname) {
                return true;
            }
        }, isRecursive);
    }

    public static List<File> listFilesInDirWithFilter(final String dirPath, final FileFilter filter) {
        return listFilesInDirWithFilter(getFileByPath(dirPath), filter, false);
    }

    public static List<File> listFilesInDirWithFilter(final File dir, final FileFilter filter) {
        return listFilesInDirWithFilter(dir, filter, false);
    }

    public static List<File> listFilesInDirWithFilter(final String dirPath, final FileFilter filter, final boolean isRecursive) {
        return listFilesInDirWithFilter(getFileByPath(dirPath), filter, isRecursive);
    }

    public static List<File> listFilesInDirWithFilter(final File dir, final FileFilter filter, final boolean isRecursive) {
        if (!isDir(dir)) return null;
        List<File> list = new ArrayList<>();
        File[] files = dir.listFiles();
        if (files != null && files.length != 0) {
            for (File file : files) {
                if (filter.accept(file)) {
                    list.add(file);
                }
                if (isRecursive && file.isDirectory()) {
                    //noinspection ConstantConditions
                    list.addAll(listFilesInDirWithFilter(file, filter, true));
                }
            }
        }
        return list;
    }

    /*------------------------------------- 增删改方法 ----------------------------------------*/

    public static boolean createOrExistsDir(final String dirPath) {
        return createOrExistsDir(getFileByPath(dirPath));
    }

    /**
     * 判断指定的文件是否存在，如果不存在就创建它
     *
     * @param file 指定的文件
     * @return 该文件是否存在，true 表示存在
     */
    public static boolean createOrExistsFile(final File file) {
        if (file == null) return false;
        if (file.exists()) return file.isFile();
        // 判断父目录是否是文件夹，如果不存在就创建它
        if (!createOrExistsDir(file.getParentFile())) return false;
        try {
            // 创建文件
            return file.createNewFile();
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }

    public static boolean createFileByDeleteOldFile(final String filePath) {
        return createFileByDeleteOldFile(getFileByPath(filePath));
    }

    /**
     * Create a file if it doesn't exist, otherwise delete old file before creating.
     *
     * @param file The file.
     * @return {@code true}: success<br>{@code false}: fail
     */
    public static boolean createFileByDeleteOldFile(final File file) {
        if (file == null) return false;
        // file exists and unsuccessfully delete then return false
        if (file.exists() && !file.delete()) return false;
        if (!createOrExistsDir(file.getParentFile())) return false;
        try {
            return file.createNewFile();
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }

    public static boolean rename(final File file, final String newName) {
        // file is null then return false
        if (file == null) return false;
        // file doesn't exist then return false
        if (!file.exists()) return false;
        // the new name is space then return false
        if (StringUtils.isSpace(newName)) return false;
        // the new name equals old name then return true
        if (newName.equals(file.getName())) return true;
        File newFile = new File(file.getParent() + File.separator + newName);
        // the new name of file exists then return false
        return !newFile.exists() && file.renameTo(newFile);
    }

    public static boolean copyFile(final String srcFilePath, final String destFilePath) {
        return copyFile(getFileByPath(srcFilePath), getFileByPath(destFilePath));
    }

    public static boolean copyFile(final String srcFilePath, final String destFilePath, final OnReplaceListener listener) {
        return copyFile(getFileByPath(srcFilePath), getFileByPath(destFilePath), listener);
    }

    public static boolean copyFile(final File srcFile, final File destFile) {
        return copyOrMoveFile(srcFile, destFile, false);
    }

    public static boolean copyFile(final File srcFile, final File destFile, final OnReplaceListener listener) {
        return copyOrMoveFile(srcFile, destFile, listener, false);
    }

    public static boolean moveFile(final String srcFilePath, final String destFilePath) {
        return moveFile(getFileByPath(srcFilePath), getFileByPath(destFilePath));
    }

    public static boolean moveFile(final String srcFilePath, final String destFilePath, final OnReplaceListener listener) {
        return moveFile(getFileByPath(srcFilePath), getFileByPath(destFilePath), listener);
    }

    public static boolean moveFile(final File srcFile, final File destFile) {
        return copyOrMoveFile(srcFile, destFile, true);
    }

    public static boolean moveFile(final File srcFile, final File destFile, final OnReplaceListener listener) {
        return copyOrMoveFile(srcFile, destFile, listener, true);
    }

    public static boolean copyDir(final String srcDirPath, final String destDirPath) {
        return copyDir(getFileByPath(srcDirPath), getFileByPath(destDirPath));
    }

    public static boolean copyDir(final String srcDirPath, final String destDirPath, final OnReplaceListener listener) {
        return copyDir(getFileByPath(srcDirPath), getFileByPath(destDirPath), listener);
    }

    public static boolean copyDir(final File srcDir, final File destDir) {
        return copyOrMoveDir(srcDir, destDir, false);
    }

    public static boolean copyDir(final File srcDir, final File destDir, final OnReplaceListener listener) {
        return copyOrMoveDir(srcDir, destDir, listener, false);
    }

    public static boolean moveDir(final String srcDirPath, final String destDirPath) {
        return moveDir(getFileByPath(srcDirPath), getFileByPath(destDirPath));
    }

    public static boolean moveDir(final String srcDirPath, final String destDirPath, final OnReplaceListener listener) {
        return moveDir(getFileByPath(srcDirPath), getFileByPath(destDirPath), listener);
    }

    public static boolean moveDir(final File srcDir, final File destDir) {
        return copyOrMoveDir(srcDir, destDir, true);
    }

    public static boolean moveDir(final File srcDir, final File destDir, final OnReplaceListener listener) {
        return copyOrMoveDir(srcDir, destDir, listener, true);
    }

    public static boolean delete(final String filePath) {
        return delete(getFileByPath(filePath));
    }

    public static boolean delete(final File file) {
        if (file == null) return false;
        if (file.isDirectory()) {
            return deleteDir(file);
        }
        return deleteFile(file);
    }

    public static boolean deleteDir(final String dirPath) {
        return deleteDir(getFileByPath(dirPath));
    }

    public static boolean deleteDir(final File dir) {
        if (dir == null) return false;
        // dir doesn't exist then return true
        if (!dir.exists()) return true;
        // dir isn't a directory then return false
        if (!dir.isDirectory()) return false;
        File[] files = dir.listFiles();
        if (files != null && files.length != 0) {
            for (File file : files) {
                if (file.isFile()) {
                    if (!file.delete()) return false;
                } else if (file.isDirectory()) {
                    if (!deleteDir(file)) return false;
                }
            }
        }
        return dir.delete();
    }

    public static boolean deleteFile(final String srcFilePath) {
        return deleteFile(getFileByPath(srcFilePath));
    }

    public static boolean deleteFile(final File file) {
        return file != null && (!file.exists() || file.isFile() && file.delete());
    }

    public static boolean deleteAllInDir(final String dirPath) {
        return deleteAllInDir(getFileByPath(dirPath));
    }

    public static boolean deleteAllInDir(final File dir) {
        return deleteFilesInDirWithFilter(dir, new FileFilter() {
            @Override
            public boolean accept(File pathname) {
                return true;
            }
        });
    }

    public static boolean deleteFilesInDir(final String dirPath) {
        return deleteFilesInDir(getFileByPath(dirPath));
    }

    public static boolean deleteFilesInDir(final File dir) {
        return deleteFilesInDirWithFilter(dir, new FileFilter() {
            @Override
            public boolean accept(File pathname) {
                return pathname.isFile();
            }
        });
    }

    public static boolean deleteFilesInDirWithFilter(final String dirPath, final FileFilter filter) {
        return deleteFilesInDirWithFilter(getFileByPath(dirPath), filter);
    }

    public static boolean deleteFilesInDirWithFilter(final File dir, final FileFilter filter) {
        if (dir == null) return false;
        // dir doesn't exist then return true
        if (!dir.exists()) return true;
        // dir isn't a directory then return false
        if (!dir.isDirectory()) return false;
        File[] files = dir.listFiles();
        if (files != null && files.length != 0) {
            for (File file : files) {
                if (filter.accept(file)) {
                    if (file.isFile()) {
                        if (!file.delete()) return false;
                    } else if (file.isDirectory()) {
                        if (!deleteDir(file)) return false;
                    }
                }
            }
        }
        return true;
    }

    public interface OnReplaceListener {
        boolean onReplace();
    }

    /*------------------------------------- inner methods ---------------------------------------*/

    private static boolean createOrExistsDir(final File file) {
        return file != null && (file.exists() ? file.isDirectory() : file.mkdirs());
    }

    private static boolean copyOrMoveFile(final File srcFile, final File destFile, final boolean isMove) {
        return copyOrMoveFile(srcFile, destFile, new OnReplaceListener() {
            @Override
            public boolean onReplace() {
                return true;
            }
        }, isMove);
    }

    private static boolean copyOrMoveFile(final File srcFile, final File destFile, final OnReplaceListener listener, final boolean isMove) {
        if (srcFile == null || destFile == null) return false;
        // srcFile equals destFile then return false
        if (srcFile.equals(destFile)) return false;
        // srcFile doesn't exist or isn't a file then return false
        if (!srcFile.exists() || !srcFile.isFile()) return false;
        if (destFile.exists()) {
            if (listener == null || listener.onReplace()) {// require delete the old file
                if (!destFile.delete()) {// unsuccessfully delete then return false
                    return false;
                }
            } else {
                return true;
            }
        }
        if (!createOrExistsDir(destFile.getParentFile())) return false;
        try {
            return writeFileFromIS(destFile, new FileInputStream(srcFile)) && !(isMove && !deleteFile(srcFile));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            return false;
        }
    }

    private static boolean copyOrMoveDir(final File srcDir, final File destDir, final boolean isMove) {
        return copyOrMoveDir(srcDir, destDir, new OnReplaceListener() {
            @Override
            public boolean onReplace() {
                return true;
            }
        }, isMove);
    }

    private static boolean copyOrMoveDir(final File srcDir, final File destDir, final OnReplaceListener listener, final boolean isMove) {
        if (srcDir == null || destDir == null) return false;
        // destDir's path locate in srcDir's path then return false
        String srcPath = srcDir.getPath() + File.separator;
        String destPath = destDir.getPath() + File.separator;
        if (destPath.contains(srcPath)) return false;
        if (!srcDir.exists() || !srcDir.isDirectory()) return false;
        if (destDir.exists()) {
            if (listener == null || listener.onReplace()) {// require delete the old directory
                if (!deleteAllInDir(destDir)) {// unsuccessfully delete then return false
                    return false;
                }
            } else {
                return true;
            }
        }
        if (!createOrExistsDir(destDir)) return false;
        File[] files = srcDir.listFiles();
        for (File file : files) {
            File oneDestFile = new File(destPath + file.getName());
            if (file.isFile()) {
                if (!copyOrMoveFile(file, oneDestFile, listener, isMove)) return false;
            } else if (file.isDirectory()) {
                if (!copyOrMoveDir(file, oneDestFile, listener, isMove)) return false;
            }
        }
        return !isMove || deleteDir(srcDir);
    }

    private static boolean writeFileFromIS(final File file, final InputStream is) {
        OutputStream os = null;
        try {
            os = new BufferedOutputStream(new FileOutputStream(file));
            byte data[] = new byte[8192];
            int len;
            while ((len = is.read(data, 0, 8192)) != -1) {
                os.write(data, 0, len);
            }
            return true;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                if (os != null) {
                    os.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private static boolean isExternalStorageDocument(Uri uri) {
        return "com.android.externalstorage.documents".equals(uri.getAuthority());
    }

    private static boolean isDownloadsDocument(Uri uri) {
        return "com.android.providers.downloads.documents".equals(uri.getAuthority());
    }

    private static boolean isMediaDocument(Uri uri) {
        return "com.android.providers.media.documents".equals(uri.getAuthority());
    }

    @Nullable
    private static String getDataColumn(Context context, Uri uri, String selection, String[] selectionArgs) {
        Cursor cursor = null;
        final String column = "_data";
        final String[] projection = {column};
        try {
            cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs, null);
            if (cursor != null && cursor.moveToFirst()) {
                final int column_index = cursor.getColumnIndexOrThrow(column);
                return cursor.getString(column_index);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (cursor != null) {
                cursor.close();
            }
        }
        return null;
    }

    private static Uri createURI(String type){
        switch (type) {
            case "image":
                return MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
            case "video":
                return  MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
            case "audio":
                return  MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
            default:
                break;
        }
        return null;
    }

    private static String byte2FitMemorySize(final long byteNum) {
        if (byteNum < 0) {
            return "shouldn't be less than zero!";
        } else if (byteNum < 1024) {
            return String.format(Locale.getDefault(), "%.3fB", (double) byteNum);
        } else if (byteNum < 1048576) {
            return String.format(Locale.getDefault(), "%.3fKB", (double) byteNum / 1024);
        } else if (byteNum < 1073741824) {
            return String.format(Locale.getDefault(), "%.3fMB", (double) byteNum / 1048576);
        } else {
            return String.format(Locale.getDefault(), "%.3fGB", (double) byteNum / 1073741824);
        }
    }

    private FileUtils() {
        throw new UnsupportedOperationException("u can't initialize me!");
    }
}