final MustacheFactory mf = new DefaultMustacheFactory();
[...]
    private Mustache initMustache() {
        log.debug("Compiling mustache with '{}'", this.templatePath);
        String templateXml = getTemplateString();
        return mf.compile(new StringReader(templateXml), this.templatePath);
    }

    private String getTemplateString() {
        String templateXml;
        try (BufferedReader br = new BufferedReader(new InputStreamReader(this.templateInputStream))) {
            templateXml = br.lines().collect(Collectors.joining("\n"));
        } catch (IOException e) {
            String message = "Cannot read template from '" + this.templateInputStream + "'";
            throw new UncheckedIOException(message, e);
        }
        return templateXml;
    }


/*********************** AFTER ********************************/

    private Mustache getInitializedMustache() {
        log.debug("Compiling mustache with '{}'", templatePath);
        return Try.withResources(this::readerOfInputStream)
                .of(this::stringWithNewlineFromReader)
                .map(StringReader::new)
                .map(stringReader -> mf.compile(stringReader, templatePath))
                .getOrElseThrow(this::mustacheInitException);
    }

    private String stringWithNewlineFromReader(BufferedReader reader) {
        return reader
                .lines()
                .collect(Collectors.joining("\n"));
    }

    private BufferedReader readerOfInputStream() {
        return new BufferedReader(new InputStreamReader(this.templateInputStream));
    }

    private MustacheException mustacheInitException(Throwable throwable) {
        return new MustacheException(
                "Cannot init mustache template from '" + this.templatePath + "'",
                throwable
        );
    }