Java 11 and 12 – New Features

Passing inferred variables to a method

Though the use of var is limited to the declaration of local variables, these variables (both primitive and reference) can be passed to methods as values. The inferred types and the types expected by the methods must match, to allow the code to compile.

In the following example code, the Child class implements the MarathonRunner interface. The start() method in the Marathon class expects the MarathonRunner object (the instances of the class implementing this interface) as its method argument. The inferred type of the aRunner variable is Child. Since the Child class implements MarathonRunner, aRunner can be passed to the start() method, the inferred type of aRunner (Child) and the expected type of start() ...