### Question:
FileHelper { public static boolean existsFile (@Nullable final File aFile) { return aFile != null && aFile.isFile (); } private  FileHelper(); static boolean existsFile(@Nullable final File aFile); static boolean existsDir(@Nullable final File aDir); static boolean canReadAndWriteFile(@Nullable final File aFile); @Nonnull static EChange ensureParentDirectoryIsPresent(@Nonnull final File aFile); @Nullable static File getCanonicalFile(@Nullable final File aFile); @Nullable static File getCanonicalFileOrNull(@Nullable final File aFile); @Nullable static String getCanonicalPath(@Nullable final File aFile); @Nullable static String getCanonicalPathOrNull(@Nullable final File aFile); @SuppressFBWarnings ("IL_INFINITE_LOOP") static boolean isParentDirectory(@Nonnull final File aSearchDirectory, @Nonnull final File aStartDirectory); @Nullable static FileInputStream getInputStream(@Nonnull final File aFile); @Nullable static NonBlockingBufferedInputStream getBufferedInputStream(@Nonnull final File aFile); @Nullable static InputStreamReader getReader(@Nonnull final File aFile, @Nonnull final Charset aCharset); @Nullable static NonBlockingBufferedReader getBufferedReader(@Nonnull final File aFile, @Nonnull final Charset aCharset); @Nullable static FileOutputStream getOutputStream(@Nonnull final File aFile); @Nullable static FileOutputStream getOutputStream(@Nonnull final File aFile, @Nonnull final EAppend eAppend); @Nullable static NonBlockingBufferedOutputStream getBufferedOutputStream(@Nonnull final File aFile); @Nullable static NonBlockingBufferedOutputStream getBufferedOutputStream(@Nonnull final File aFile, @Nonnull final EAppend eAppend); @Nullable static OutputStreamWriter getWriter(@Nonnull final File aFile, @Nonnull final Charset aCharset); @Nullable static OutputStreamWriter getWriter(@Nonnull final File aFile, @Nonnull final EAppend eAppend, @Nonnull final Charset aCharset); @Nullable static NonBlockingBufferedWriter getBufferedWriter(@Nonnull final File aFile, @Nonnull final Charset aCharset); @Nullable static NonBlockingBufferedWriter getBufferedWriter(@Nonnull final File aFile,
                                                             @Nonnull final EAppend eAppend,
                                                             @Nonnull final Charset aCharset); @Nullable static PrintWriter getPrintWriter(@Nonnull final File aFile, @Nonnull final Charset aCharset); @Nullable static PrintWriter getPrintWriter(@Nonnull final File aFile, @Nonnull final EAppend eAppend, @Nonnull final Charset aCharset); @Nullable static RandomAccessFile getRandomAccessFile(@Nonnull final String sFilename, @Nonnull final ERandomAccessFileMode eMode); @Nullable static RandomAccessFile getRandomAccessFile(@Nonnull final File aFile, @Nonnull final ERandomAccessFileMode eMode); static boolean isFileNewer(@Nonnull final File aFile1, @Nonnull final File aFile2); @Nonnull static String getFileSizeDisplay(@Nullable final File aFile); @Nonnull static String getFileSizeDisplay(@Nullable final File aFile, @Nonnegative final int nDecimals); @Nonnull static String getFileSizeDisplay(final long nFileSize); @Nonnull static String getFileSizeDisplay(@Nonnegative final long nFileSize, @Nonnegative final int nDecimals); @Nullable static File getSecureFile(@Nullable final File aFile); @Nonnegative static int getDirectoryObjectCount(@Nonnull final File aDirectory); @Nonnull @ReturnsMutableCopy static ICommonsList <File> getDirectoryContent(@Nonnull final File aDirectory); @Nonnull @ReturnsMutableCopy static ICommonsList <File> getDirectoryContent(@Nonnull final File aDirectory, @Nonnull final FilenameFilter aFilenameFilter); @Nonnull @ReturnsMutableCopy static ICommonsList <File> getDirectoryContent(@Nonnull final File aDirectory, @Nonnull final FileFilter aFileFilter); @Nullable static URL getAsURL(@Nonnull final File aFile); @Nullable static String getAsURLString(@Nonnull final File aFile);  }### Answer:
@Test public void testExistsFile () { assertFalse (FileHelper.existsFile (new File ("oaaajeee"))); assertTrue (FileHelper.existsFile (ClassPathResource.getAsFile ("streamutils-lines"))); assertFalse (FileHelper.existsFile (new File ("src"))); }