public Iterable<? extends CompilationUnitTree> parse() throws IOException {
        try {
            prepareCompiler();
            List<JCCompilationUnit> units = compiler.parseFiles(fileObjects);
            for (JCCompilationUnit unit: units) {
                JavaFileObject file = unit.getSourceFile();
                if (notYetEntered.containsKey(file))
                    notYetEntered.put(file, unit);
            }
            return units;
        }
        finally {
            parsed = true;
            if (compiler != null && compiler.log != null)
                compiler.log.flush();
        }
    }