code: public static Method findKnownMethod(Class<?> aClass,
                                           String name,
                                           Class<?>... paramTypes)
      {
          try
          {
              return aClass.getMethod(name, paramTypes);
          }
          catch (NoSuchMethodException ex)
          {
              // This cannot happen if the method is correctly identified.
              throw new IllegalArgumentException("Method " + name + " does not exist in class " + aClass.getName(), ex);
          }
      }
docs: Looks up a method that is explicitly identified.  This method should only
  be used for methods that definitely exist.  It does not throw the checked
  NoSuchMethodException.  If the method does not exist, it will instead fail
  with an unchecked IllegalArgumentException.
  @param aClass The class in which the method exists.
  @param name The name of the method.
  @param paramTypes The types of the method's parameters.
  @return The identified method.