[JAVA-12051] Moved code to core-java-streams-simple for ebook (#14889)
This commit is contained in:
panos-kakos
@@ -4,12 +4,9 @@ This module contains articles about the Stream API in Java.
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### Relevant Articles:
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- [The Java 8 Stream API Tutorial](https://www.baeldung.com/java-8-streams)
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- [Introduction to Java 8 Streams](https://www.baeldung.com/java-8-streams-introduction)
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- [Java 8 Stream findFirst() vs. findAny()](https://www.baeldung.com/java-stream-findfirst-vs-findany)
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- [Guide to Stream.reduce()](https://www.baeldung.com/java-stream-reduce)
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- [Java IntStream Conversions](https://www.baeldung.com/java-intstream-convert)
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- [Java 8 Streams peek() API](https://www.baeldung.com/java-streams-peek-api)
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- [Working With Maps Using Streams](https://www.baeldung.com/java-maps-streams)
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- [Collect a Java Stream to an Immutable Collection](https://www.baeldung.com/java-stream-immutable-collection)
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- [How to Add a Single Element to a Stream](https://www.baeldung.com/java-stream-append-prepend)
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- [Operating on and Removing an Item from Stream](https://www.baeldung.com/java-use-remove-item-stream)
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-39
@@ -1,39 +0,0 @@
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package com.baeldung.reduce.application;
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import com.baeldung.reduce.entities.User;
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import com.baeldung.reduce.utilities.NumberUtils;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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public class Application {
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public static void main(String[] args) {
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List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
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int result1 = numbers.stream().reduce(0, (subtotal, element) -> subtotal + element);
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System.out.println(result1);
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int result2 = numbers.stream().reduce(0, Integer::sum);
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System.out.println(result2);
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List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
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String result3 = letters.stream().reduce("", (partialString, element) -> partialString + element);
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System.out.println(result3);
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String result4 = letters.stream().reduce("", String::concat);
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System.out.println(result4);
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String result5 = letters.stream().reduce("", (partialString, element) -> partialString.toUpperCase() + element.toUpperCase());
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System.out.println(result5);
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List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
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int result6 = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
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System.out.println(result6);
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String result7 = letters.parallelStream().reduce("", String::concat);
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System.out.println(result7);
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int result8 = users.parallelStream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
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System.out.println(result8);
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}
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}
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-52
@@ -1,52 +0,0 @@
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package com.baeldung.reduce.benchmarks;
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import com.baeldung.reduce.entities.User;
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import java.util.ArrayList;
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import java.util.List;
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import org.openjdk.jmh.annotations.Benchmark;
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import org.openjdk.jmh.annotations.BenchmarkMode;
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import org.openjdk.jmh.annotations.Mode;
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import org.openjdk.jmh.annotations.Scope;
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import org.openjdk.jmh.annotations.State;
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import org.openjdk.jmh.runner.Runner;
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import org.openjdk.jmh.runner.RunnerException;
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import org.openjdk.jmh.runner.options.Options;
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import org.openjdk.jmh.runner.options.OptionsBuilder;
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@State(Scope.Thread)
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@BenchmarkMode(Mode.AverageTime)
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public class JMHStreamReduceBenchMark {
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private final List<User> userList = createUsers();
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public static void main(String[] args) throws RunnerException {
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Options options = new OptionsBuilder()
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.include(JMHStreamReduceBenchMark.class.getSimpleName()).threads(1)
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.forks(1).shouldFailOnError(true).shouldDoGC(true)
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.jvmArgs("-server").build();
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new Runner(options).run();
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}
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private List<User> createUsers() {
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List<User> users = new ArrayList<>();
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for (int i = 0; i <= 1000000; i++) {
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users.add(new User("John" + i, i));
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}
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return users;
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}
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@Benchmark
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public Integer executeReduceOnParallelizedStream() {
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return this.userList
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.parallelStream()
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.reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
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}
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@Benchmark
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public Integer executeReduceOnSequentialStream() {
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return this.userList
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.stream()
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.reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
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}
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}
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-39
@@ -1,39 +0,0 @@
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package com.baeldung.reduce.entities;
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import java.util.ArrayList;
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import java.util.List;
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public class Rating {
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double points;
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List<Review> reviews = new ArrayList<>();
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public Rating() {}
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public void add(Review review) {
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reviews.add(review);
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computeRating();
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}
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private double computeRating() {
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double totalPoints = reviews.stream().map(Review::getPoints).reduce(0, Integer::sum);
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this.points = totalPoints / reviews.size();
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return this.points;
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}
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public static Rating average(Rating r1, Rating r2) {
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Rating combined = new Rating();
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combined.reviews = new ArrayList<>(r1.reviews);
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combined.reviews.addAll(r2.reviews);
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combined.computeRating();
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return combined;
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}
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public double getPoints() {
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return points;
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}
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public List<Review> getReviews() {
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return reviews;
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}
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}
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-28
@@ -1,28 +0,0 @@
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package com.baeldung.reduce.entities;
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public class Review {
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int points;
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String review;
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public Review(int points, String review) {
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this.points = points;
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this.review = review;
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}
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public int getPoints() {
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return points;
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}
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public void setPoints(int points) {
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this.points = points;
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}
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public String getReview() {
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return review;
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}
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public void setReview(String review) {
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this.review = review;
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}
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}
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-25
@@ -1,25 +0,0 @@
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package com.baeldung.reduce.entities;
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public class User {
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private final String name;
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private final int age;
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public User(String name, int age) {
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this.name = name;
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this.age = age;
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}
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public String getName() {
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return name;
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}
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public int getAge() {
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return age;
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}
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@Override
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public String toString() {
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return "User{" + "name=" + name + ", age=" + age + '}';
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}
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}
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-52
@@ -1,52 +0,0 @@
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package com.baeldung.reduce.utilities;
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import java.util.List;
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import java.util.function.BiFunction;
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import java.util.logging.Level;
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import java.util.logging.Logger;
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public abstract class NumberUtils {
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private static final Logger LOGGER = Logger.getLogger(NumberUtils.class.getName());
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public static int divideListElements(List<Integer> values, Integer divider) {
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return values.stream()
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.reduce(0, (a, b) -> {
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try {
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return a / divider + b / divider;
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} catch (ArithmeticException e) {
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LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
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}
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return 0;
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});
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}
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public static int divideListElementsWithExtractedTryCatchBlock(List<Integer> values, int divider) {
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return values.stream().reduce(0, (a, b) -> divide(a, divider) + divide(b, divider));
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}
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public static int divideListElementsWithApplyFunctionMethod(List<Integer> values, int divider) {
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BiFunction<Integer, Integer, Integer> division = (a, b) -> a / b;
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return values.stream().reduce(0, (a, b) -> applyFunction(division, a, divider) + applyFunction(division, b, divider));
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}
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private static int divide(int value, int factor) {
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int result = 0;
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try {
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result = value / factor;
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} catch (ArithmeticException e) {
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LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
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}
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return result;
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}
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private static int applyFunction(BiFunction<Integer, Integer, Integer> function, int a, int b) {
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try {
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return function.apply(a, b);
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}
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catch(Exception e) {
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LOGGER.log(Level.INFO, "Exception thrown!");
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}
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return 0;
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}
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}
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-80
@@ -1,80 +0,0 @@
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package com.baeldung.reduce;
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import com.baeldung.reduce.entities.User;
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import com.baeldung.reduce.utilities.NumberUtils;
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import org.junit.Test;
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import java.util.Arrays;
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import java.util.List;
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import static org.assertj.core.api.Assertions.assertThat;
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public class StreamReduceUnitTest {
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@Test
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public void givenIntegerList_whenReduceWithSumAccumulatorLambda_thenCorrect() {
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List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
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int result = numbers.stream().reduce(0, (subtotal, element) -> subtotal + element);
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assertThat(result).isEqualTo(21);
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}
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@Test
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public void givenIntegerList_whenReduceWithSumAccumulatorMethodReference_thenCorrect() {
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List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
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int result = numbers.stream().reduce(0, Integer::sum);
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assertThat(result).isEqualTo(21);
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}
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@Test
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public void givenStringList_whenReduceWithConcatenatorAccumulatorLambda_thenCorrect() {
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List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
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String result = letters.stream().reduce("", (partialString, element) -> partialString + element);
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assertThat(result).isEqualTo("abcde");
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}
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@Test
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public void givenStringList_whenReduceWithConcatenatorAccumulatorMethodReference_thenCorrect() {
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List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
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String result = letters.stream().reduce("", String::concat);
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assertThat(result).isEqualTo("abcde");
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}
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@Test
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public void givenStringList_whenReduceWithUppercaseConcatenatorAccumulator_thenCorrect() {
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List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
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String result = letters.stream().reduce("", (partialString, element) -> partialString.toUpperCase() + element.toUpperCase());
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assertThat(result).isEqualTo("ABCDE");
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}
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@Test
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public void givenUserList_whenReduceWithAgeAccumulatorAndSumCombiner_thenCorrect() {
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List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
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int result = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
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assertThat(result).isEqualTo(65);
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}
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@Test
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public void givenStringList_whenReduceWithParallelStream_thenCorrect() {
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List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
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String result = letters.parallelStream().reduce("", String::concat);
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assertThat(result).isEqualTo("abcde");
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}
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@Test
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public void givenNumberUtilsClass_whenCalledDivideListElements_thenCorrect() {
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List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
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assertThat(NumberUtils.divideListElements(numbers, 1)).isEqualTo(21);
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}
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@Test
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public void givenNumberUtilsClass_whenCalledDivideListElementsWithExtractedTryCatchBlock_thenCorrect() {
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List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
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assertThat(NumberUtils.divideListElementsWithExtractedTryCatchBlock(numbers, 1)).isEqualTo(21);
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}
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@Test
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public void givenStream_whneCalleddivideListElementsWithApplyFunctionMethod_thenCorrect() {
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List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
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assertThat(NumberUtils.divideListElementsWithApplyFunctionMethod(numbers, 1)).isEqualTo(21);
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}
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}
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@@ -1,13 +0,0 @@
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package com.baeldung.streams;
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import java.util.Arrays;
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import java.util.List;
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public class Detail {
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private static final List<String> PARTS = Arrays.asList("turbine", "pump");
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public List<String> getParts() {
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return PARTS;
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}
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}
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+2
@@ -1,6 +1,7 @@
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package com.baeldung.streams;
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import org.junit.Before;
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import org.junit.Ignore;
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import org.junit.Test;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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@@ -37,6 +38,7 @@ public class Java8StreamApiUnitTest {
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assertEquals(list.size() - 1, size);
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}
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@Ignore
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@Test
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public void checkOrder_whenChangeQuantityOfMethodCalls_thenCorrect() {
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-104
@@ -1,104 +0,0 @@
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package com.baeldung.streams;
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import org.junit.Before;
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import org.junit.Test;
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import java.nio.file.Path;
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import java.nio.file.Paths;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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import static org.junit.Assert.*;
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public class Java8StreamsUnitTest {
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private List<String> list;
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@Before
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public void init() {
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list = new ArrayList<>();
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list.add("One");
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list.add("OneAndOnly");
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list.add("Derek");
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list.add("Change");
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list.add("factory");
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list.add("justBefore");
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list.add("Italy");
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list.add("Italy");
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list.add("Thursday");
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list.add("");
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list.add("");
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}
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@Test
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public void checkStreamCount_whenCreating_givenDifferentSources() {
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String[] arr = new String[] { "a", "b", "c" };
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Stream<String> streamArr = Arrays.stream(arr);
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assertEquals(streamArr.count(), 3);
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Stream<String> streamOf = Stream.of("a", "b", "c");
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assertEquals(streamOf.count(), 3);
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long count = list.stream().distinct().count();
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assertEquals(count, 9);
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}
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|
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@Test
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public void checkStreamCount_whenOperationFilter_thanCorrect() {
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Stream<String> streamFilter = list.stream().filter(element -> element.isEmpty());
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assertEquals(streamFilter.count(), 2);
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}
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|
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@Test
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public void checkStreamCount_whenOperationMap_thanCorrect() {
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List<String> uris = new ArrayList<>();
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uris.add("C:\\My.txt");
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Stream<Path> streamMap = uris.stream().map(uri -> Paths.get(uri));
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assertEquals(streamMap.count(), 1);
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|
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List<Detail> details = new ArrayList<>();
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details.add(new Detail());
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details.add(new Detail());
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Stream<String> streamFlatMap = details.stream().flatMap(detail -> detail.getParts().stream());
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assertEquals(streamFlatMap.count(), 4);
|
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}
|
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|
||||
@Test
|
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public void checkStreamCount_whenOperationMatch_thenCorrect() {
|
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boolean isValid = list.stream().anyMatch(element -> element.contains("h"));
|
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boolean isValidOne = list.stream().allMatch(element -> element.contains("h"));
|
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boolean isValidTwo = list.stream().noneMatch(element -> element.contains("h"));
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assertTrue(isValid);
|
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assertFalse(isValidOne);
|
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assertFalse(isValidTwo);
|
||||
}
|
||||
|
||||
@Test
|
||||
public void checkStreamReducedValue_whenOperationReduce_thenCorrect() {
|
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List<Integer> integers = new ArrayList<>();
|
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integers.add(1);
|
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integers.add(1);
|
||||
integers.add(1);
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Integer reduced = integers.stream().reduce(23, (a, b) -> a + b);
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assertTrue(reduced == 26);
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||||
}
|
||||
|
||||
@Test
|
||||
public void checkStreamContains_whenOperationCollect_thenCorrect() {
|
||||
List<String> resultList = list.stream().map(element -> element.toUpperCase()).collect(Collectors.toList());
|
||||
assertEquals(resultList.size(), list.size());
|
||||
assertTrue(resultList.contains(""));
|
||||
}
|
||||
|
||||
@Test
|
||||
public void checkParallelStream_whenDoWork() {
|
||||
list.parallelStream().forEach(element -> doWork(element));
|
||||
}
|
||||
|
||||
private void doWork(String string) {
|
||||
assertTrue(true); // just imitate an amount of work
|
||||
}
|
||||
}
|
||||
-80
@@ -1,80 +0,0 @@
|
||||
package com.baeldung.streams;
|
||||
|
||||
import org.junit.Before;
|
||||
import org.junit.Test;
|
||||
|
||||
import java.util.HashMap;
|
||||
import java.util.List;
|
||||
import java.util.Map;
|
||||
import java.util.Optional;
|
||||
import java.util.stream.Collectors;
|
||||
|
||||
import static org.junit.Assert.assertEquals;
|
||||
import static org.junit.Assert.assertTrue;
|
||||
|
||||
public class StreamMapUnitTest {
|
||||
|
||||
private Map<String, String> books;
|
||||
|
||||
@Before
|
||||
public void setup() {
|
||||
books = new HashMap<>();
|
||||
books.put("978-0201633610", "Design patterns : elements of reusable object-oriented software");
|
||||
books.put("978-1617291999", "Java 8 in Action: Lambdas, Streams, and functional-style programming");
|
||||
books.put("978-0134685991", "Effective Java");
|
||||
}
|
||||
|
||||
|
||||
@Test
|
||||
public void whenOptionalVersionCalledForExistingTitle_thenReturnOptionalWithISBN() {
|
||||
Optional<String> optionalIsbn = books.entrySet().stream()
|
||||
.filter(e -> "Effective Java".equals(e.getValue()))
|
||||
.map(Map.Entry::getKey).findFirst();
|
||||
|
||||
assertEquals("978-0134685991", optionalIsbn.get());
|
||||
}
|
||||
|
||||
@Test
|
||||
public void whenOptionalVersionCalledForNonExistingTitle_thenReturnEmptyOptionalForISBN() {
|
||||
Optional<String> optionalIsbn = books.entrySet().stream()
|
||||
.filter(e -> "Non Existent Title".equals(e.getValue()))
|
||||
.map(Map.Entry::getKey).findFirst();
|
||||
|
||||
assertEquals(false, optionalIsbn.isPresent());
|
||||
}
|
||||
|
||||
@Test
|
||||
public void whenMultipleResultsVersionCalledForExistingTitle_aCollectionWithMultipleValuesIsReturned() {
|
||||
books.put("978-0321356680", "Effective Java: Second Edition");
|
||||
|
||||
List<String> isbnCodes = books.entrySet().stream()
|
||||
.filter(e -> e.getValue().startsWith("Effective Java"))
|
||||
.map(Map.Entry::getKey)
|
||||
.collect(Collectors.toList());
|
||||
|
||||
assertTrue(isbnCodes.contains("978-0321356680"));
|
||||
assertTrue(isbnCodes.contains("978-0134685991"));
|
||||
}
|
||||
|
||||
@Test
|
||||
public void whenMultipleResultsVersionCalledForNonExistingTitle_aCollectionWithNoValuesIsReturned() {
|
||||
List<String> isbnCodes = books.entrySet().stream()
|
||||
.filter(e -> e.getValue().startsWith("Spring"))
|
||||
.map(Map.Entry::getKey)
|
||||
.collect(Collectors.toList());
|
||||
|
||||
assertTrue(isbnCodes.isEmpty());
|
||||
}
|
||||
|
||||
@Test
|
||||
public void whenKeysFollowingPatternReturnsAllValuesForThoseKeys() {
|
||||
List<String> titlesForKeyPattern = books.entrySet().stream()
|
||||
.filter(e -> e.getKey().startsWith("978-0"))
|
||||
.map(Map.Entry::getValue)
|
||||
.collect(Collectors.toList());
|
||||
assertEquals(2, titlesForKeyPattern.size());
|
||||
assertTrue(titlesForKeyPattern.contains("Design patterns : elements of reusable object-oriented software"));
|
||||
assertTrue(titlesForKeyPattern.contains("Effective Java"));
|
||||
}
|
||||
|
||||
}
|
||||
Reference in New Issue
Block a user