code: public static Class<?>[] wrappersToPrimitives(Class<?>[] classes) {
          if (classes == null) {
              return null;
          }
          if (classes.length == 0) {
              return classes;
          }
  
          Class<?>[] convertedClasses = new Class<?>[classes.length];
          for (int i = 0; i < classes.length; i++) {
              convertedClasses[i] = wrapperToPrimitive(classes[i]);
          }
          return convertedClasses;
      }
docs: <p>Converts the specified array of wrapper Class objects to an array of
  its corresponding primitive Class objects.</p>
  
  <p>This method invokes <code>wrapperToPrimitive()</code> for each element
  of the passed in array.</p>
  
  @param classes  the class array to convert, may be null or empty
  @return an array which contains for each given class, the primitive class or
  <b>null</b> if the original class is not a wrapper class. <code>null</code> if null input.
  Empty array if an empty array passed in.
  @see #wrapperToPrimitive(Class)