Java 11 and 12 – New Features

Adding var to lambda parameters

Java allows for the use of the reserved word var with lambda parameters, to align its syntax with the declaration of local variables, which can now use var.

Let's modify the examples from the preceding section, adding var to the lambda parameters:

(var age) -> age > 10; 
(var age) -> age > 10? "Kid" : "Not a Kid"; 
(var age) -> {System.out.println();}; () -> {return Math.random() + "Number";}; 
 
(var name, var list) -> { 
                             return ( 
                                 list.stream() 
                                     .filter(e ->                                       e.getName().startsWith(name)) 
                                     .map(Person::getAge) 
                                     .findFirst() 
                                 ); 
                             }; 

The main reason for allowing the addition of var to lambda parameters is to align the usage with the syntax of the local parameters declared using var.

If you are using var with lambda parameters, ...