Test if object is instanceof a parameter type

The only way you can do this check is if you have the Class object representing the type:

Class<T> type; //maybe passed into the method
if ( type.isInstance(obj) ) {
   //...
}

To extend the sample of Mark Peters, often you want to do something like:

Class<T> type; //maybe passed to the method
if ( type.isInstance(obj) ) {
   T t = type.cast(obj);
   // ...
}

If you don't want to pass Class type as a parameter as mentioned by Mark Peters, you can use the following code. Kudos to David O'Meara.

  Class<T> type = (Class<T>) ((ParameterizedType) getClass().getGenericSuperclass())
                  .getActualTypeArguments()[0];
  if (type.isInstance(obj)) {
      ...
  }