src/main/java/com/github/fge/grappa/Grappa.java
public static <P extends BaseParser<V>, V> P createParser(
        @Nonnull final Class<P> parserClass, final Object... constructorArgs)
    {
        Objects.requireNonNull(parserClass, "parserClass");
        try {
            final Class<?> extendedClass
                = ParserTransformer.transformParser(parserClass);
            final Constructor<?> constructor
                = findConstructor(extendedClass, constructorArgs);
            @SuppressWarnings("unchecked")
            final P ret = (P) constructor.newInstance(constructorArgs);
            return ret;
        } catch (Exception e) { // TODO: catch better than Exception
            throw new RuntimeException(
                "Error creating extended parser class: " + e.getMessage(), e);
        }
    }
public static <P extends BaseParser<V>, V> P createParser(
        @Nonnull final Class<P> parserClass, final Object... constructorArgs)
    {
        Objects.requireNonNull(parserClass, "parserClass");
        try {
            final Class<?> extendedClass
                = ParserTransformer.transformParser(parserClass);
            final Constructor<?> constructor
                = findConstructor(extendedClass, constructorArgs);
            @SuppressWarnings("unchecked")
            final P ret = (P) constructor.newInstance(constructorArgs);
            return ret;
        } catch (Exception e) { // TODO: catch better than Exception
            throw new RuntimeException(
                "Error creating extended parser class: " + e.getMessage(), e);
        }
    }
<p>Creates a parser object whose rule creation methods can then be used
with one of the {@link ParseRunner} implementations.</p>
<p>Since parboiled needs to extend your parser with certain extra logic
(e.g. to prevent infinite recursions in recursive rule definitions) you
cannot create your parser object yourself, but have to go through this
method. Also your parser class has to be derived from {@link BaseParser}.
If you want to use a non-default constructor you can provide its
arguments to this method. Make sure your non-default constructor does not
use primitive type parameters (like "int") but rather their boxed
counterparts (like "Integer"), otherwise the constructor will not be
found.</p>
<p>Performing the rule analysis and extending the parser class is an
expensive process (time-wise) and can take up to several hundred
milliseconds for large grammars. However, this cost is only incurred once
per parser class and class loader. Subsequent calls to this method are
therefore fast once the initial extension has been performed.</p>

@param parserClass the type of the parser to create
@param constructorArgs optional arguments to the parser class constructor
@return the ready to use parser instance