code: public void defineFunction(String prefix, String function, Method method)
              throws java.lang.NoSuchMethodException {
  
          if (prefix == null || function == null || method == null) {
              throw new NullPointerException(Util.message(
                      context, "elProcessor.defineFunctionNullParams"));
          }
  
          int modifiers = method.getModifiers();
  
          // Check for public method as well as being static
          if (!Modifier.isStatic(modifiers) || !Modifier.isPublic(modifiers)) {
              throw new NoSuchMethodException(Util.message(context,
                      "elProcessor.defineFunctionInvalidMethod", method.getName(),
                      method.getDeclaringClass().getName()));
          }
  
          manager.mapFunction(prefix, function, method);
      }
docs: Map a method to a function name.
  
  @param prefix    Function prefix
  @param function  Function name
  @param method    Method
  
  @throws NullPointerException
  If any of the arguments are null
  @throws NoSuchMethodException
  If the method is not static