FileUtil { public static String readLink(File f) { if (f == null) { LOG.warn("Can not read a null symLink"); return ""; } try { return Shell.execCommand( Shell.getReadlinkCommand(f.toString())).trim(); } catch (IOException x) { return ""; } }  static Path[] stat2Paths(FileStatus[] stats); static Path[] stat2Paths(FileStatus[] stats, Path path); static void fullyDeleteOnExit(final File file); static boolean fullyDelete(final File dir); static boolean fullyDelete(final File dir, boolean tryGrantPermissions); static String readLink(File f); static boolean fullyDeleteContents(final File dir); static boolean fullyDeleteContents(final File dir, final boolean tryGrantPermissions); @Deprecated static void fullyDelete(FileSystem fs, Path dir); static boolean copy(FileSystem srcFS, Path src,
                             FileSystem dstFS, Path dst,
                             boolean deleteSource,
                             Configuration conf); static boolean copy(FileSystem srcFS, Path[] srcs,
                             FileSystem dstFS, Path dst,
                             boolean deleteSource,
                             boolean overwrite, Configuration conf); static boolean copy(FileSystem srcFS, Path src,
                             FileSystem dstFS, Path dst,
                             boolean deleteSource,
                             boolean overwrite,
                             Configuration conf); static boolean copy(FileSystem srcFS, FileStatus srcStatus,
                             FileSystem dstFS, Path dst,
                             boolean deleteSource,
                             boolean overwrite,
                             Configuration conf); static boolean copy(File src,
                             FileSystem dstFS, Path dst,
                             boolean deleteSource,
                             Configuration conf); static boolean copy(FileSystem srcFS, Path src,
                             File dst, boolean deleteSource,
                             Configuration conf); static String makeShellPath(String filename); static String makeShellPath(File file); static String makeSecureShellPath(File file); static String makeShellPath(File file, boolean makeCanonicalPath); static long getDU(File dir); static void unZip(InputStream inputStream, File toDir); static void unZip(File inFile, File unzipDir); static void unTar(InputStream inputStream, File untarDir,
                           boolean gzipped); static void unTar(File inFile, File untarDir); static int symLink(String target, String linkname); static int chmod(String filename, String perm
                          ); static int chmod(String filename, String perm, boolean recursive); static void setOwner(File file, String username,
      String groupname); static boolean setReadable(File f, boolean readable); static boolean setWritable(File f, boolean writable); static boolean setExecutable(File f, boolean executable); static boolean canRead(File f); static boolean canWrite(File f); static boolean canExecute(File f); static void setPermission(File f, FsPermission permission
                                   ); static final File createLocalTempFile(final File basefile,
                                               final String prefix,
                                               final boolean isDeleteOnExit); static void replaceFile(File src, File target); static File[] listFiles(File dir); static String[] list(File dir); static String[] createJarWithClassPath(String inputClassPath, Path pwd,
      Map<String, String> callerEnv); static String[] createJarWithClassPath(String inputClassPath, Path pwd,
      Path targetDir,
      Map<String, String> callerEnv); static List<Path> getJarsInDirectory(String path); static List<Path> getJarsInDirectory(String path, boolean useLocal); static boolean compareFs(FileSystem srcFs, FileSystem destFs); static FileSystem write(final FileSystem fs, final Path path,
      final byte[] bytes); static FileContext write(final FileContext fileContext,
      final Path path, final byte[] bytes); static FileSystem write(final FileSystem fs, final Path path,
      final Iterable<? extends CharSequence> lines, final Charset cs); static FileContext write(final FileContext fileContext,
      final Path path, final Iterable<? extends CharSequence> lines,
      final Charset cs); static FileSystem write(final FileSystem fs, final Path path,
      final CharSequence charseq, final Charset cs); static FileContext write(final FileContext fs, final Path path,
      final CharSequence charseq, final Charset cs); static FileSystem write(final FileSystem fs, final Path path,
      final CharSequence charseq); static FileContext write(final FileContext fileContext,
      final Path path, final CharSequence charseq); static final int SYMLINK_NO_PRIVILEGE; }
@Test public void testReadSymlinkWithNullInput() { String result = FileUtil.readLink(null); Assert.assertEquals("", result); }
@Test public void testReadSymlinkWithAFileAsInput() throws IOException { File file = new File(del, FILE); String result = FileUtil.readLink(file); Assert.assertEquals("", result); file.delete(); }