Java Reference
In-Depth Information
Key Points
▪ A lambda expression is a method without a name that is used to pass around behavior as
if it were data.
▪ Lambda expressions look like this:
BinaryOperator<Integer> add = (x, y) → x +
y
.
▪ A functional interface is an interface with a single abstract method that is used as the
type of a lambda expression.
Exercises
At the end of each chapter is a series of exercises to give you an opportunity to practice what
you've learned during the chapter and help you learn the new concepts. The answers to these
Example 2-15. The function functional interface
public
public interface
interface
Function
Function
<
T
,
R
> {
R
apply
(
T t
);
}
a. Can you draw this functional interface diagrammatically?
b. What kind of lambda expressions might you use this functional interface for if
you were writing a software calculator?
c. Which of these lambda expressions are valid
Function<Long,Long>
imple-
mentations?
x
->
x
+
1
;
(
x
,
y
) ->
x
+
1
;
x
->
x
==
1
;
2.
ThreadLocal lambda expressions
. Java has a class called
ThreadLocal
that acts as a
container for a value that's local to your current thread. In Java 8 there is a new fact-
