if (!GUtil.isTrue(path)) {
            throw new IllegalArgumentException(String.format(
                "path may not be null or empty string. path='%s'", path));
        }

        File file = convertObjectToFile(path);

        if (file == null) {
            throw new IllegalArgumentException(String.format("Cannot convert path to File. path='%s'", path));
        }

        if (!file.isAbsolute()) {

        if (shouldVisit(details)) {
            if (attrs.isSymbolicLink()) {
                // when FileVisitOption.FOLLOW_LINKS, we only get here when link couldn't be followed
                throw new GradleException(String.format("Couldn't follow symbolic link '%s'.", file));
            }
            visitor.visitFile(details);
        }
        return checkStopFlag();
    }

        } catch (Exception e) {
            throw new CopyFileElementException(String.format("Could not copy %s to '%s'.", getDisplayName(), target), e);
        }
    }

    private void validateTimeStamps() {
        final long lastModified = getLastModified();
        if(lastModified < 0) {
            throw new GradleException(String.format("Invalid Timestamp %s for '%s'.", lastModified, getDisplayName()));
        }
    }

        for (int u = 0; u <=7; u++) {
            for (int g = 0; g <= 7; g++) {
                for (int o = 0; o <= 7; o++) {
                    String numericNotation = String.format("%d%d%d", u, g, o);
                    int mode = u * 64 + g * 8 + o;
                    assertEquals(mode, newUnixPermission(numericNotation).toUnixNumeric());
                }
            }
        }
    }

        throw new InvalidUserDataException(String.format("Cannot convert URL '%s' to a file.", converted));
    }

    protected void validate(File file, PathValidation validation) {
        switch (validation) {
            case NONE:
                break;
            case EXISTS:
                if (!file.exists()) {
                    throw new InvalidUserDataException(String.format("File '%s' does not exist.", file));

        File file = convertObjectToFile(path);

        if (file == null) {
            throw new IllegalArgumentException(String.format(
                "Cannot convert path to File. path='%s'", path));
        }

        if (!file.isAbsolute()) {
            throw new UnsupportedOperationException(String.format("Cannot convert relative path %s to an absolute file.", path));
        }
        return file;
    }

    @Override

                if (!file.canRead()) {
                    throw new GradleException(String.format("Could not list contents of directory '%s' as it is not readable.", file));
                }
                // else, might be a link which points to nothing, or has been removed while we're visiting, or ...
                throw new GradleException(String.format("Could not list contents of '%s'.", file));
            }

        List<Object> classNames = CollectionUtils.collect(Cast.<Class<?>[]>uncheckedNonnullCast(closure.getParameterTypes()), Class::getName);
        return String.format(
                "The closure '%s' is not valid as an action for argument '%s'. It should accept no parameters, or one compatible with type '%s'. It accepts (%s).",

            visitor.accept(sourceTree);
        }
    }

    public void addToUnion(FileCollection source) {
        if (!(source instanceof FileTree)) {
            throw new UnsupportedOperationException(String.format("Can only add FileTree instances to %s.", getDisplayName()));
        }

        sourceTrees.add(Cast.cast(FileTreeInternal.class, source));
    }

        String destDir = "";
        if (args.length > 3) {
            destDir = args[3];
        }

        System.out.format("=> stylesheet %s%n", stylesheet);
        System.out.format("=> source %s%n", source);
        System.out.format("=> dest %s%n", dest);
        System.out.format("=> destDir %s%n", destDir);

        TransformerFactory factory = TransformerFactory.newInstance();