::new in Java

[Nandhini Sridharan]

public static void main( String[] args ) {
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Defaulable defaulable = DefaulableFactory.create( DefaultableImpl::new );
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System.out.println( defaulable.notRequired() );
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defaulable = DefaulableFactory.create( OverridableImpl::new );
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System.out.println( defaulable.notRequired() );
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}

I recently came across the above code in one of the article. Though I understand that ::new is used to pass the instance of the class. I would love to really read and understand about ::new. Can someone has any article links about it?

[Nandhini Sridharan]

Okay this is basically as part of method reference. While DefaultableImpl::new refers to constructor reference of DefaultableImpl class.

Thanks.

[Campbell Ritchie]

It is like writing new Foo. In a λ you can write Foo::new instead.

[Rob Spoor]

Depending on the functional interface used for DefaulableFactory.create, DefaultableImpl::new can mean one of several things:

- If create takes a Supplier or Callable, it means () -> new DefaultableImpl().
- If create takes a Function (IntFunction, LongFunction, DoubleFunction), it means t -> new DefaultableImpl(t).
- If create takes a BiFunction, it means (t, u) -> new DefaultableImpl(t, u).

There are more out-of-the-box functional interfaces, and there can be even more, but you should get the picture.

[Rahul Mahindrakar]

Hi

If it helps

Here is the link to this part in Java Tutorial

https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html

[Steve Beckle]

I've found this link to be a good one for what you're looking for. http://winterbe.com/posts/2014/03/16/java-8-tutorial/