How can I use reference method in a UnaryOperator java 8

Question

Currently, I have a UnaryOperator like this

UnaryOperator<Object> defaultParser = obj -> obj;

I don't know if I can use a method reference in these kinds of operation. Example:

UnaryOperator<String> defaultParser = String::toString;

But with the generic way, not just String .

Answer 1

If you just want to avoid the lambda expression, UnaryOperator has static identity() method:

UnaryOperator<Object> defaultParser = UnaryOperator.identity();

If you specifically want a method reference (why??), you can define a method in your class

public static <T> T identity(T t) {
    return t;
}

Then you will be able to use it as a method reference:

UnaryOperator<Object> defaultParser = MyClass::identity;

Answer 2

Yes, you can using the UnaryOperator.identity() as:

UnaryOperator<Object> defaultParser = UnaryOperator.identity();

which is defined with a lambda expression as

static <T> UnaryOperator<T> identity() {
    return t -> t;
}