Init commit all code

2021-09-23 15:03:44 -04:00
parent 32311cd138
commit 1a634bdd03
49 changed files with 2165 additions and 0 deletions
@@ -0,0 +1,9 @@
+package com.baeldung.aspect;
+
+public aspect ChangeCallsToCurrentTimeInMillisMethod {
+    long around():
+            call(public static native long java.lang.System.currentTimeMillis())
+                    && within(user.code.base.pckg.*) {
+        return 0;
+    }
+}
@@ -0,0 +1,14 @@
+package com.ossez.java_8_features;
+
+public class Address {
+
+    private String street;
+
+    public String getStreet() {
+        return street;
+    }
+
+    public void setStreet(String street) {
+        this.street = street;
+    }
+}
@@ -0,0 +1,4 @@
+package com.ossez.java_8_features;
+
+public class CustomException extends RuntimeException {
+}
@@ -0,0 +1,16 @@
+package com.ossez.java_8_features;
+
+import java.util.Optional;
+
+public class OptionalAddress {
+
+    private String street;
+
+    public Optional<String> getStreet() {
+        return Optional.ofNullable(street);
+    }
+
+    public void setStreet(String street) {
+        this.street = street;
+    }
+}
@@ -0,0 +1,16 @@
+package com.ossez.java_8_features;
+
+import java.util.Optional;
+
+public class OptionalUser {
+
+    private OptionalAddress address;
+
+    public Optional<OptionalAddress> getAddress() {
+        return Optional.of(address);
+    }
+
+    public void setAddress(OptionalAddress address) {
+        this.address = address;
+    }
+}
@@ -0,0 +1,40 @@
+package com.ossez.java_8_features;
+
+import java.util.Optional;
+
+public class User {
+
+    private String name;
+
+    private Address address;
+
+    public Address getAddress() {
+        return address;
+    }
+
+    public void setAddress(Address address) {
+        this.address = address;
+    }
+
+    public User() {
+    }
+
+    public User(String name) {
+        this.name = name;
+    }
+
+    public static boolean isRealUser(User user) {
+        return true;
+    }
+
+    public String getOrThrow() {
+        String value = null;
+        Optional<String> valueOpt = Optional.ofNullable(value);
+        String result = valueOpt.orElseThrow(CustomException::new).toUpperCase();
+        return result;
+    }
+
+    public boolean isLegalName(String name) {
+        return name.length() > 3 && name.length() < 16;
+    }
+}
@@ -0,0 +1,18 @@
+package com.ossez.java_8_features;
+
+public interface Vehicle {
+
+    void moveTo(long altitude, long longitude);
+
+    static String producer() {
+        return "N&F Vehicles";
+    }
+
+    default long[] startPosition() {
+        return new long[] { 23, 15 };
+    }
+
+    default String getOverview() {
+        return "ATV made by " + producer();
+    }
+}
@@ -0,0 +1,9 @@
+package com.ossez.java_8_features;
+
+public class VehicleImpl implements Vehicle {
+
+    @Override
+    public void moveTo(long altitude, long longitude) {
+        // do nothing
+    }
+}
@@ -0,0 +1,36 @@
+package com.ossez.java_8_features.groupingby;
+
+public class BlogPost {
+    private String title;
+    private String author;
+    private BlogPostType type;
+    private int likes;
+
+    public BlogPost(String title, String author, BlogPostType type, int likes) {
+        this.title = title;
+        this.author = author;
+        this.type = type;
+        this.likes = likes;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public String getAuthor() {
+        return author;
+    }
+
+    public BlogPostType getType() {
+        return type;
+    }
+
+    public int getLikes() {
+        return likes;
+    }
+
+    @Override
+    public String toString() {
+        return "BlogPost{" + "title='" + title + '\'' + ", type=" + type + ", likes=" + likes + '}';
+    }
+}
@@ -0,0 +1,5 @@
+package com.ossez.java_8_features.groupingby;
+
+public enum BlogPostType {
+    NEWS, REVIEW, GUIDE
+}
@@ -0,0 +1,41 @@
+package com.ossez.java_8_features.groupingby;
+
+import java.util.Objects;
+
+public class Tuple {
+    private final BlogPostType type;
+    private final String author;
+
+    public Tuple(BlogPostType type, String author) {
+        this.type = type;
+        this.author = author;
+    }
+
+    public BlogPostType getType() {
+        return type;
+    }
+
+    public String getAuthor() {
+        return author;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        Tuple tuple = (Tuple) o;
+        return type == tuple.type && author.equals(tuple.author);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(type, author);
+    }
+
+    @Override
+    public String toString() {
+        return "Tuple{" + "type=" + type + ", author='" + author + '\'' + '}';
+    }
+}
@@ -0,0 +1,19 @@
+package com.ossez.nullsafecollectionstreams;
+
+import java.util.Collection;
+import java.util.stream.Stream;
+import static org.apache.commons.collections4.CollectionUtils.emptyIfNull;
+
+public class NullSafeCollectionStreamsUsingCommonsEmptyIfNull {
+
+    /**
+    * This method shows how to make a null safe stream from a collection through the use of 
+    * emptyIfNull() method from Apache Commons CollectionUtils library
+    * 
+     * @param collection The collection that is to be converted into a stream
+     * @return The stream that has been created from the collection or an empty stream if the collection is null
+    */
+    public Stream<String> collectionAsStream(Collection<String> collection) {
+        return emptyIfNull(collection).stream();
+    }
+}
@@ -0,0 +1,21 @@
+package com.ossez.nullsafecollectionstreams;
+
+import java.util.Collection;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+public class NullSafeCollectionStreamsUsingJava8OptionalContainer {
+
+    /**
+    * This method shows how to make a null safe stream from a collection  through the use of 
+    * Java SE 8’s Optional Container
+    * 
+     * @param collection The collection that is to be converted into a stream
+     * @return The stream that has been created from the collection or an empty stream if the collection is null
+    */
+    public Stream<String> collectionAsStream(Collection<String> collection) {
+        return Optional.ofNullable(collection)
+            .map(Collection::stream)
+            .orElseGet(Stream::empty);
+    }
+}
@@ -0,0 +1,20 @@
+package com.ossez.nullsafecollectionstreams;
+
+import java.util.Collection;
+import java.util.stream.Stream;
+
+public class NullSafeCollectionStreamsUsingNullDereferenceCheck {
+    
+    /**
+    * This method shows how to make a null safe stream from a collection through the use of a check 
+    * to prevent null dereferences
+    * 
+    * @param collection The collection that is to be converted into a stream
+    * @return The stream that has been created from the collection or an empty stream if the collection is null
+    */
+    public Stream<String> collectionAsStream(Collection<String> collection) {
+        return collection == null ? Stream.empty() : collection.stream();
+    }    
+
+
+}
@@ -0,0 +1,44 @@
+package com.ossez.spliteratorAPI;
+
+import java.util.List;
+
+public class Article {
+    private List<Author> listOfAuthors;
+    private int id;
+    private String name;
+
+    public Article(String name) {
+        this.name = name;
+    }
+
+    public Article(List<Author> listOfAuthors, int id) {
+        super();
+        this.listOfAuthors = listOfAuthors;
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public List<Author> getListOfAuthors() {
+        return listOfAuthors;
+    }
+
+    public void setListOfAuthors(List<Author> listOfAuthors) {
+        this.listOfAuthors = listOfAuthors;
+    }
+
+}
@@ -0,0 +1,33 @@
+package com.ossez.spliteratorAPI;
+
+public class Author {
+    private String name;
+    private int relatedArticleId;
+
+    public Author(String name, int relatedArticleId) {
+        this.name = name;
+        this.relatedArticleId = relatedArticleId;
+    }
+
+    public int getRelatedArticleId() {
+        return relatedArticleId;
+    }
+
+    public void setRelatedArticleId(int relatedArticleId) {
+        this.relatedArticleId = relatedArticleId;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public String toString() {
+        return "[name: " + name + ", relatedId: " + relatedArticleId + "]";
+    }
+}
+
@@ -0,0 +1,19 @@
+package com.ossez.spliteratorAPI;
+
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class Executor {
+
+	public static int countAutors(Stream<Author> stream) {
+		RelatedAuthorCounter wordCounter = stream.reduce(new RelatedAuthorCounter(0, true),
+				RelatedAuthorCounter::accumulate, RelatedAuthorCounter::combine);
+		return wordCounter.getCounter();
+	}
+
+	public static List<Article> generateElements() {
+		return Stream.generate(() -> new Article("Java")).limit(35000).collect(Collectors.toList());
+	}
+
+}
@@ -0,0 +1,27 @@
+package com.ossez.spliteratorAPI;
+
+public class RelatedAuthorCounter {
+    private final int counter;
+    private final boolean isRelated;
+
+    public RelatedAuthorCounter(int counter, boolean isRelated) {
+        this.counter = counter;
+        this.isRelated = isRelated;
+    }
+
+    public RelatedAuthorCounter accumulate(Author author) {
+        if (author.getRelatedArticleId() == 0) {
+            return isRelated ? this : new RelatedAuthorCounter(counter, true);
+        } else {
+            return isRelated ? new RelatedAuthorCounter(counter + 1, false) : this;
+        }
+    }
+
+    public RelatedAuthorCounter combine(RelatedAuthorCounter RelatedAuthorCounter) {
+        return new RelatedAuthorCounter(counter + RelatedAuthorCounter.counter, RelatedAuthorCounter.isRelated);
+    }
+
+    public int getCounter() {
+        return counter;
+    }
+}
@@ -0,0 +1,49 @@
+package com.ossez.spliteratorAPI;
+
+import java.util.List;
+import java.util.Spliterator;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Consumer;
+
+public class RelatedAuthorSpliterator implements Spliterator<Author> {
+	private final List<Author> list;
+	AtomicInteger current = new AtomicInteger();
+
+	public RelatedAuthorSpliterator(List<Author> list) {
+		this.list = list;
+	}
+
+	@Override
+	public boolean tryAdvance(Consumer<? super Author> action) {
+
+		action.accept(list.get(current.getAndIncrement()));
+		return current.get() < list.size();
+	}
+
+	@Override
+	public Spliterator<Author> trySplit() {
+		int currentSize = list.size() - current.get();
+		if (currentSize < 10) {
+			return null;
+		}
+		for (int splitPos = currentSize / 2 + current.intValue(); splitPos < list.size(); splitPos++) {
+			if (list.get(splitPos).getRelatedArticleId() == 0) {
+				Spliterator<Author> spliterator = new RelatedAuthorSpliterator(list.subList(current.get(), splitPos));
+				current.set(splitPos);
+				return spliterator;
+			}
+		}
+		return null;
+	}
+
+	@Override
+	public long estimateSize() {
+		return list.size() - current.get();
+	}
+
+	@Override
+	public int characteristics() {
+		return CONCURRENT;
+	}
+
+}
@@ -0,0 +1,27 @@
+package com.ossez.spliteratorAPI;
+
+import java.util.Spliterator;
+import java.util.concurrent.Callable;
+
+public class Task implements Callable<String> {
+    private Spliterator<Article> spliterator;
+    private final static String SUFFIX = "- published by Baeldung";
+
+    public Task(Spliterator<Article> spliterator) {
+        this.spliterator = spliterator;
+    }
+
+    @Override
+    public String call() {
+        int current = 0;
+        while (spliterator.tryAdvance(article -> {
+            article.setName(article.getName()
+                .concat(SUFFIX));
+        })) {
+            current++;
+        }
+        ;
+        return Thread.currentThread()
+            .getName() + ":" + current;
+    }
+}
@@ -0,0 +1,11 @@
+package com.ossez.strategy;
+
+import java.math.BigDecimal;
+
+public class ChristmasDiscounter implements Discounter {
+
+    @Override
+    public BigDecimal apply(BigDecimal amount) {
+        return amount.multiply(BigDecimal.valueOf(0.9));
+    }
+}
@@ -0,0 +1,23 @@
+package com.ossez.strategy;
+
+import java.math.BigDecimal;
+import java.util.function.UnaryOperator;
+
+public interface Discounter extends UnaryOperator<BigDecimal> {
+
+    default Discounter combine(Discounter after) {
+        return value -> after.apply(this.apply(value));
+    }
+
+    static Discounter christmas() {
+        return (amount) -> amount.multiply(BigDecimal.valueOf(0.9));
+    }
+
+    static Discounter newYear() {
+        return (amount) -> amount.multiply(BigDecimal.valueOf(0.8));
+    }
+
+    static Discounter easter() {
+        return (amount) -> amount.multiply(BigDecimal.valueOf(0.5));
+    }
+}
@@ -0,0 +1,11 @@
+package com.ossez.strategy;
+
+import java.math.BigDecimal;
+
+public class EasterDiscounter implements Discounter {
+
+    @Override
+    public BigDecimal apply(BigDecimal amount) {
+        return amount.multiply(BigDecimal.valueOf(0.5));
+    }
+}
@@ -0,0 +1,63 @@
+package com.ossez.streamreduce.application;
+
+import com.ossez.streamreduce.entities.User;
+import com.ossez.streamreduce.utilities.NumberUtils;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class Application {
+
+    public static void main(String[] args) {
+        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6);
+        int result1 = numbers.stream().reduce(0, (a, b) -> a + b);
+        System.out.println(result1);
+        
+        int result2 = numbers.stream().reduce(0, Integer::sum);
+        System.out.println(result2);
+
+        List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
+        String result3 = letters.stream().reduce("", (a, b) -> a + b);
+        System.out.println(result3);
+        
+        String result4 = letters.stream().reduce("", String::concat);
+        System.out.println(result4);
+
+        String result5 = letters.stream().reduce("", (a, b) -> a.toUpperCase() + b.toUpperCase());
+        System.out.println(result5);
+        
+        List<User> users = Arrays.asList(new User("John", 30), new User("Julie", 35));
+        int result6 = users.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        System.out.println(result6);
+        
+        String result7 = letters.parallelStream().reduce("", String::concat);
+        System.out.println(result7);
+        
+        int result8 = users.parallelStream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        System.out.println(result8);
+        
+        List<User> userList = new ArrayList<>();
+        for (int i = 0; i <= 1000000; i++) {
+            userList.add(new User("John" + i, i));
+        }
+        
+        long t1 = System.currentTimeMillis();
+        int result9 = userList.stream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        long t2 = System.currentTimeMillis();
+        System.out.println(result9);
+        System.out.println("Sequential stream time: " + (t2 - t1) + "ms");
+        
+        long t3 = System.currentTimeMillis();
+        int result10 = userList.parallelStream().reduce(0, (partialAgeResult, user) -> partialAgeResult + user.getAge(), Integer::sum);
+        long t4 = System.currentTimeMillis();
+        System.out.println(result10);
+        System.out.println("Parallel stream time: " + (t4 - t3) + "ms");
+        
+        int result11 = NumberUtils.divideListElements(numbers, 1);
+        System.out.println(result11);
+        
+        int result12 = NumberUtils.divideListElementsWithExtractedTryCatchBlock(numbers, 0);
+        System.out.println(result12);
+    }    
+}
@@ -0,0 +1,39 @@
+package com.ossez.streamreduce.entities;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Rating {
+
+    double points;
+    List<Review> reviews = new ArrayList<>();
+
+    public Rating() {}
+
+    public void add(Review review) {
+        reviews.add(review);
+        computeRating();
+    }
+
+    private double computeRating() {
+        double totalPoints = reviews.stream().map(Review::getPoints).reduce(0, Integer::sum);
+        this.points = totalPoints / reviews.size();
+        return this.points;
+    }
+
+    public static Rating average(Rating r1, Rating r2) {
+        Rating combined = new Rating();
+        combined.reviews = new ArrayList<>(r1.reviews);
+        combined.reviews.addAll(r2.reviews);
+        combined.computeRating();
+        return combined;
+    }
+
+    public double getPoints() {
+        return points;
+    }
+
+    public List<Review> getReviews() {
+        return reviews;
+    }
+}
@@ -0,0 +1,28 @@
+package com.ossez.streamreduce.entities;
+
+public class Review {
+
+    int points;
+    String review;
+
+    public Review(int points, String review) {
+        this.points = points;
+        this.review = review;
+    }
+
+    public int getPoints() {
+        return points;
+    }
+
+    public void setPoints(int points) {
+        this.points = points;
+    }
+
+    public String getReview() {
+        return review;
+    }
+
+    public void setReview(String review) {
+        this.review = review;
+    }
+}
@@ -0,0 +1,30 @@
+package com.ossez.streamreduce.entities;
+
+public class User {
+
+    private final String name;
+    private final int age;
+    private final Rating rating = new Rating();
+
+    public User(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public Rating getRating() {
+        return rating;
+    }
+
+    @Override
+    public String toString() {
+        return "User{" + "name=" + name + ", age=" + age + '}';
+    }
+}
@@ -0,0 +1,52 @@
+package com.ossez.streamreduce.utilities;
+
+import java.util.List;
+import java.util.function.BiFunction;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public abstract class NumberUtils {
+
+    private static final Logger LOGGER = Logger.getLogger(NumberUtils.class.getName());
+
+    public static int divideListElements(List<Integer> values, Integer divider) {
+        return values.stream()
+                .reduce(0, (a, b) -> {
+                    try {
+                        return a / divider + b / divider;
+                    } catch (ArithmeticException e) {
+                        LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
+                    }
+                    return 0;
+                });
+    }
+    
+    public static int divideListElementsWithExtractedTryCatchBlock(List<Integer> values, int divider) {
+        return values.stream().reduce(0, (a, b) -> divide(a, divider) + divide(b, divider));
+    }
+    
+    public static int divideListElementsWithApplyFunctionMethod(List<Integer> values, int divider) {
+        BiFunction<Integer, Integer, Integer> division = (a, b) -> a / b;
+        return values.stream().reduce(0, (a, b) -> applyFunction(division, a, divider) + applyFunction(division, b, divider));
+    }
+    
+    private static int divide(int value, int factor) {
+        int result = 0;
+        try {
+            result = value / factor;
+        } catch (ArithmeticException e) {
+            LOGGER.log(Level.INFO, "Arithmetic Exception: Division by Zero");
+        }
+        return result;
+    }
+    
+    private static int applyFunction(BiFunction<Integer, Integer, Integer> function, int a, int b) {
+        try {
+            return function.apply(a, b);
+        }
+        catch(Exception e) {
+            LOGGER.log(Level.INFO, "Exception occurred!");
+        }
+        return 0;
+    }
+}
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS}  [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="TRACE">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>