What is the type of a Java empty Optional?

So the thing is I was checking Optional Java class and I noticed this in the public static<T> Optional<T> empty() doc:

@param <T> The type of the non-existent value*.

And, after looking at the whole class and searching over here and a few other pages I came to this questions that I haven't been able to answer:

1. Can an empty Optional have a specific type?
   1.1 If so, how do you set it?
   1.2 And is there any way to check its type?

It's whatever type you specify:

// Empty Optional with value type String
Optional<String> opt = Optional.empty();

Here is the source code for that method from OpenJDK 11:

    public static<T> Optional<T> empty() {
        @SuppressWarnings("unchecked")
        Optional<T> t = (Optional<T>) EMPTY;
        return t;
    }

EMPTY is a static instance (from the source code linked above):

    /**
     * Common instance for {@code empty()}.
     */
    private static final Optional<?> EMPTY = new Optional<>();

The Optional class is a container that might contain a specific element. As such, it has two concepts:

• The type it might contain
• The actual object it contains

The type it might contain is specified trough generics. Generics only exist at compile time and are lost at runtime.

To answer your questions:

1. When using an Optional, you usually define it to possibly contain a type, like this:

Optional<String> optionalString;

At this point we know that optionalString might contain a String. If we do this:

Optional<String> optionalString = Optional.empty();

It doesn't actually contain anything, but we can use it anywhere an Optional<String> is required.

2. The type of the Optional is inferred trough its usage. Like above, you specify the Optional.empty() to be an Optional<String>. You can also specify its type trough the return value of a method, like so:

public Optional<Integer> findNumber() {
    return Optional.empty();
}

3. Since the type is no longer present at runtime, there is no way to check what the optional contains at this point. At runtime, an empty Optional has no type.

I know a Link to a Blogpost has already been posted, but I always refer back to this on: Baeldung Java Optional 8

To ur questions:

1. Optional can contain any Object type(if u need an int then use Integer)

2. Optional.of(urObject) now the "type" is Optional<typeOfUrObject>

3. No u can't check the type of the Optional.