Test if object is instanceof a parameter type

Is there a way to determine if an object is an instance of a generic type?

public <T> test(Object obj) {
    if (obj instanceof T) {
        ...
    }
}

That clearly doesn't work. Is there an alternative? Like I want to use Java reflection to instantiate a class and then check to make sure it is of type generic T.

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)) {
      ...
  }

You could try this,

// Cast your object to the generic type.
T data = null;
try {
    data = (T) obj;
} catch (ClassCastException cce) {
    // Log the error.
}

// Check if the cast completed successfully.
if(data != null) {
    // whatever....
}

It would make more sense to put the restriction on where the type T is used to parametrise the Class type. When you pass the type in, instead of using something like Class<?>, you should use Class<? extends T>.

This will only work (partly) if you have an object of type T. Then you can get the class of that object, see java.lang.Class<T> and find if it's the same as the object in question.

But note that this goes counter the very reason we have genrics: using a generic type is a way to say that you don't care what type it really is (up to upper and lower bounds that may be specified).