How does this java code instantiate an abstract class?

I'm changing our Java class, and I notice the following line of code:

OurClass<OurInterface1> ourClass = new OurClass<OurInterface1>() {};

What I find strange about this line is that ourclass is an abstract class - here is the definition of ourclass:

public abstract class OurClass<T extends OurInterface1> implements OurInterface2<T>

When I delete {} at the end of the line, eclipse tells me that the type ourclass < ourinterface1 > cannot be instantiated, but when I put {} back, everything is normal

How does {} allow you to instantiate an abstract class?

Solution

Add {} to introduce the syntax of anonymous inner class

You are declaring an anonymous inner class, which is a subclass of ourclass The body of this class is empty: {} This anonymous inner class is not abstract, so you can instantiate it

When you delete {}, the compiler thinks you directly instantiate an abstract class ourclass, so it does not allow it