dtonhofer
Functional Programming in Java, Second Edition: Code for "Chapter 7, Lazy Evaluations" in one file
Nothing special:
package chapter7;
import org.junit.jupiter.api.Test;
import java.util.List;
import java.util.function.Supplier;
import java.util.stream.Stream;
public class BeingLazy_LazyEvaluations {
private final static List<String> names = List.of("Brad", "Kate", "Kim", "Jack", "Joe", "Mike", "Susan", "George", "Robert", "Julia", "Parker", "Benson");
// "lazy/fpij/Evaluation.java" on p. 127, p.128
private static boolean evaluate(final int value) {
System.out.println("evaluating ..." + value);
simulateTimeConsumingOp(2000);
return value > 100;
}
private static void simulateTimeConsumingOp(long time_ms) {
try {
Thread.sleep(time_ms);
} catch (InterruptedException ex) {
throw new RuntimeException(ex);
}
}
// "lazy/fpij/Evaluation.java" p. 127
private static void eagerEvaluator(final boolean input1, final boolean input2) {
System.out.println("eagerEvaluator called...");
System.out.println("accept?: " + (input1 && input2));
}
// "lazy/fpij/Evaluation.java" p. 128
private static void lazyEvaluator(final Supplier<Boolean> input1, final Supplier<Boolean> input2) {
System.out.println("lazyEvaluator called...");
System.out.println("accept?: " + (input1.get() && input2.get()));
}
// "lazy/fpij/LazyStreams.java" on p.130
private static int length(final String name) {
System.out.println("getting length for " + name);
return name.length();
}
// "lazy/fpij/LazyStreams.java" on p.130
private static String toUpper(final String name) {
System.out.println("converting to uppercase: " + name);
return name.toUpperCase();
}
// "lazy/fpij/Evaluation.java" on p.127
@Test
void evaluateEagerly() {
eagerEvaluator(evaluate(1), evaluate(2));
}
// "lazy/fpij/Evaluation.java" on p.128
@Test
void evaluateLazily() {
lazyEvaluator(() -> evaluate(1), () -> evaluate(2));
}
// "lazy/fpij/LazyStreams.java" on p.130
// ".map(name -> toUpper(name))" replaced with ".map(LazyStreams::toUpper)"
@Test
void lazyStream() {
final String firstNameWith3Letters =
names.stream()
.filter(name -> length(name) == 3)
.map(BeingLazy_LazyEvaluations::toUpper)
.findFirst()
.orElse("");
System.out.println(firstNameWith3Letters);
}
// lazy/fpij/LazyStreams.java on p.132
// ".map(name -> toUpper(name))" replaced with ".map(LazyStreams::toUpper)"
@Test
void peekingIntoLaziness() {
Stream<String> namesWith3Letters =
names.stream()
.filter(name -> length(name) == 3)
.map(BeingLazy_LazyEvaluations::toUpper);
System.out.println("Stream created, filtered, mapped...");
System.out.println("ready to call findFirst...");
final String firstNameWith3Letters =
namesWith3Letters
.findFirst()
.orElse("");
System.out.println(firstNameWith3Letters);
}
}
Popular Pragmatic Bookshelf topics
Python Testing With Pytest - Chapter 2, warnings for “unregistered custom marks”
While running the smoke tests in Chapter 2, I get these...
New
Title: Hands-on Rust: question about get_component (page 295)
(feel free to respond. “You dug you’re own hole… good luck”)
I have somet...
New
Hi! I know not the intentions behind this narrative when called, on page XI:
mount() |> handle_event() |> render()
but the correc...
New
Title: Intuitive Python: docker run… denied error (page 2)
Attempted to run the docker command in both CLI and Powershell
PS C:\Users\r...
New
A Common-Sense Guide to Data Structures and Algorithms, Second Edition by Jay Wengrow @jaywengrow
Hi,
I have the paperback version of t...
New
The book has the same “Problem space/Solution space” diagram on page 18 as is on page 17. The correct Problem/Solution space diagrams ar...
New
Title: Build a Weather Station with Elixir and Nerves: Problem connecting to Postgres with Grafana on (page 64)
If you follow the defau...
New
Is the book’s epub format available to read on Google Play Books?
New
@parrt
In the context of Chapter 4.3, the grammar Java.g4, meant to parse Java 6 compilation units, no longer passes ANTLR (currently 4....
New
@mfazio23
Android Studio will not accept anything I do when trying to use the Transformations class, as described on pp. 140-141. Googl...
New
Other popular topics
Ruby, Io, Prolog, Scala, Erlang, Clojure, Haskell. With Seven Languages in Seven Weeks, by Bruce A. Tate, you’ll go beyond the syntax—and...
New
New
You might be thinking we should just ask who’s not using VSCode :joy: however there are some new additions in the space that might give V...
New
poll
poll
Be sure to check out @Dusty’s article posted here: An Introduction to Alternative Keyboard Layouts It’s one of the best write-...
New
New
Build efficient applications that exploit the unique benefits of a pure functional language, learning from an engineer who uses Haskell t...
New
Author Spotlight:
VM Brasseur
@vmbrasseur
We have a treat for you today! We turn the spotlight onto Open Source as we sit down with V...
New
I’m able to do the “artistic” part of game-development; character designing/modeling, music, environment modeling, etc.
However, I don’t...
New
Get the comprehensive, insider information you need for Rails 8 with the new edition of this award-winning classic.
Sam Ruby @rubys
...
New
Curious what kind of results others are getting, I think actually prefer the 7B model to the 32B model, not only is it faster but the qua...
New
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /wasm
- /ruby
- /erlang
- /phoenix
- /keyboards
- /python
- /js
- /rails
- /security
- /go
- /swift
- /vim
- /clojure
- /java
- /emacs
- /haskell
- /svelte
- /typescript
- /onivim
- /kotlin
- /c-plus-plus
- /crystal
- /tailwind
- /react
- /gleam
- /ocaml
- /elm
- /vscode
- /flutter
- /ash
- /html
- /deepseek
- /opensuse
- /zig
- /centos
- /php
- /scala
- /react-native
- /lisp
- /textmate
- /sublime-text
- /nixos
- /debian
- /agda
- /deno
- /django
- /kubuntu
- /arch-linux
- /nodejs
- /ubuntu
- /spring
- /revery
- /manjaro
- /julia
- /diversity
- /lua
- /markdown
- /quarkus









