Java Reference
In-Depth Information
17.3
Write a lambda or method reference for each of the following tasks:
a) Write a lambda that can be used in place of the following anonymous inner class:
new
IntConsumer()
{
public void
accept(
int
value)
{
System.out.printf(
"%d "
, value);
}
}
b) Write a method reference that can be used in place of the following lambda:
(String s) -> {
return
s.toUpperCase();}
c)
Write a no-argument lambda that implicitly returns the
String
"Welcome
to
lambdas!"
.
d)
Write a method reference for
Math
method
sqrt
.
e)
Create a one-parameter lambda that returns the cube of its argument.
Answers to Self-Review Exercises
17.1
a) functional interfaces. b) parallelize. c) internal. d)
BinaryOperator<T>
. e)
Predicate<T>
.
f ) lambda expression. g) lazy. h)
forEach
. i) Capturing. j) short circuit. k) key, value.
17.2
a) True. b) False. Terminal operations are
eager
—they perform the requested operation
when they are called. c) False. When summing the elements, the identity value is 0 and when getting
the product of the elements the identity value is 1. d) True. e) False.
Stream
method
flatMap
re-
ceives a
Function
that maps an object into a stream. f) False. Should say: “…does not override them,
…” instead of “overrides them.”
17.3
a)
value -> System.out.printf(
"%d "
, value)
b)
String::toUpperCase
c)
() ->
"Welcome to lambdas!"
d)
Math::sqrt
e)
value -> value * value * value
Exercises
17.4
Fill in the blanks in each of the following statements:
a)
Stream
are formed from stream sources, intermediate operations and terminal
operations.
b)
The following code uses the technique of
iteration:
int
sum =
0
;
for
(
int
counter =
0
; counter < values.length; counter++)
sum += values[counter];
c)
Functional programming capabilities focus on
—not modifying the data
source being processed or any other program state.
d)
The functional interface contains method
accept
that takes a
T
argument and
returns
void
;
accept
performs a task with its
T
argument, such as outputting the object,
invoking a method of the object, etc.
e)
The functional interface contains method
get
that takes no arguments and
produces a value of type
T
—this is often used to create a collection object in which a
stream operation's results are placed.
