What are curly braces after function call for?

Question

In the following code, what does Type type mean, and what are the curly brackets are used for?

Type type = new TypeToken<List<String>>(){}.getType();
List<String> list = converter.fromJson(jsonStringArray, type ); 

Answer 1

That's not after a function call, but after a constructor call. The line

Type type = new TypeToken<List<String>>(){}.getType();

is creating an instance of an anonymous subclass of TypeToken, and then calling its getType() method. You could do the same in two lines:

TypeToken<List<String>> typeToken = new TypeToken<List<String>>(){};
Type type = typeToken.getType();

The Java Tutorial Anonymous Subclasses has more examples of this. This is a somewhat peculiar usage, since no methods are being overridden, and no instance initialization block is being used. (See Initializing Fields for more about instance initialization blocks.)

Answer 2

Type is a class.

new TypeToken<List<String>>() {
}.getType();

Is creating an anonymous inner class and invoking getType() on the object created.