Merge pull request #8064 from martinvw/feature/BAEL-3292

[BAEL-3292] Add missing code snippets from the Java 8 groupingBy article

core-java-modules/core-java-8/src/main/java/com/baeldung/java_8_features/groupingby/Tuple.java

@@ -1,12 +1,12 @@
 package com.baeldung.java_8_features.groupingby;
 
-public class Tuple {
+import java.util.Objects;
+
+public class Tuple {
+    private final BlogPostType type;
+    private final String author;
 
-    private BlogPostType type;
-    private String author;
-    
     public Tuple(BlogPostType type, String author) {
-        super();
         this.type = type;
         this.author = author;
     }
@@ -15,20 +15,27 @@ public class Tuple {
         return type;
     }
 
-    public void setType(BlogPostType type) {
-        this.type = type;
-    }
-
     public String getAuthor() {
         return author;
     }
 
-    public void setAuthor(String author) {
-        this.author = 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 + ", getType()=" + getType() + ", getAuthor()=" + getAuthor() + ", getClass()=" + getClass() + ", hashCode()=" + hashCode() + ", toString()=" + super.toString() + "]";
+        return "Tuple{" + "type=" + type + ", author='" + author + '\'' + '}';
     }
 }

core-java-modules/core-java-8/src/test/java/com/baeldung/java_8_features/groupingby/Java8GroupingByCollectorUnitTest.java

@@ -1,15 +1,32 @@
 package com.baeldung.java_8_features.groupingby;
 
-import com.baeldung.java_8_features.groupingby.BlogPost;
-import com.baeldung.java_8_features.groupingby.BlogPostType;
-import org.junit.Test;
+import static java.util.Comparator.comparingInt;
+import static java.util.stream.Collectors.averagingInt;
+import static java.util.stream.Collectors.counting;
+import static java.util.stream.Collectors.groupingBy;
+import static java.util.stream.Collectors.groupingByConcurrent;
+import static java.util.stream.Collectors.joining;
+import static java.util.stream.Collectors.mapping;
+import static java.util.stream.Collectors.maxBy;
+import static java.util.stream.Collectors.summarizingInt;
+import static java.util.stream.Collectors.summingInt;
+import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.toSet;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
 
-import java.util.*;
+import java.util.Arrays;
+import java.util.EnumMap;
+import java.util.IntSummaryStatistics;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
 import java.util.concurrent.ConcurrentMap;
 
-import static java.util.Comparator.comparingInt;
-import static java.util.stream.Collectors.*;
-import static org.junit.Assert.*;
+import org.junit.Test;
 
 public class Java8GroupingByCollectorUnitTest {
 
@@ -180,4 +197,19 @@ public class Java8GroupingByCollectorUnitTest {
         assertEquals(15, newsLikeStatistics.getMin());
     }
 
+    @Test
+    public void givenAListOfPosts_whenGroupedByComplexMapKeyType_thenGetAMapBetweenTupleAndList() {
+        Map<Tuple, List<BlogPost>> postsPerTypeAndAuthor = posts.stream()
+            .collect(groupingBy(post -> new Tuple(post.getType(), post.getAuthor())));
+
+        List<BlogPost> result = postsPerTypeAndAuthor.get(new Tuple(BlogPostType.GUIDE, "Author 1"));
+
+        assertThat(result.size()).isEqualTo(1);
+
+        BlogPost blogPost = result.get(0);
+
+        assertThat(blogPost.getTitle()).isEqualTo("Programming guide");
+        assertThat(blogPost.getType()).isEqualTo(BlogPostType.GUIDE);
+        assertThat(blogPost.getAuthor()).isEqualTo("Author 1");
+    }
 }