code: public static Class<?>[] toPrimitiveType(Class<?>[] types) {
  		if (types == null) {
  			throw new IllegalArgumentException("types cannot be null");
  		}
  
  		Class<?>[] convertedTypes = new Class<?>[types.length];
  		for (int i = 0; i < types.length; i++) {
  			final Class<?> originalType = types[i];
  			Class<?> primitiveType = primitiveWrapper.get(originalType);
  			if (primitiveType == null) {
  				convertedTypes[i] = originalType;
  			} else {
  				convertedTypes[i] = primitiveType;
  			}
  		}
  		return convertedTypes;
  	}
docs: Convert all wrapper types in {@code types} to their primitive
  counter parts.
  
  @param types
  The array of types that should be converted.
  @return A new array where all wrapped types have been converted to their
  primitive counter part.