new tests

core-java-8/src/test/java/org/baeldung/java8/Java8SortUnitTest.java

@@ -1,8 +1,10 @@
 package org.baeldung.java8;
 
+import static org.baeldung.java8.entity.Human.compareByNameThenAge;
 import static org.hamcrest.Matchers.equalTo;
 
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.List;
 
 import org.baeldung.java8.entity.Human;
@@ -16,6 +18,18 @@ public class Java8SortUnitTest {
 
     // tests -
 
+    @Test
+    public final void givenPreLambda_whenSortingEntitiesByName_thenCorrectlySorted() {
+        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
+        Collections.sort(humans, new Comparator<Human>() {
+            @Override
+            public final int compare(final Human h1, final Human h2) {
+                return h1.getName().compareTo(h2.getName());
+            }
+        });
+        Assert.assertThat(humans.get(0), equalTo(new Human("Jack", 12)));
+    }
+
     @Test
     public final void whenSortingEntitiesByName_thenCorrectlySorted() {
         final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
@@ -24,10 +38,61 @@ public class Java8SortUnitTest {
     }
 
     @Test
-    public final void whenSortingEntitiesByAge_thenCorrectlySorted() {
+    public final void givenLambdaShortForm_whenSortingEntitiesByName_thenCorrectlySorted() {
         final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
-        Collections.sort(humans, (final Human h1, final Human h2) -> Ints.compare(h1.getAge(), h2.getAge()));
+        Collections.sort(humans, (h1, h2) -> h1.getName().compareTo(h2.getName()));
+        Assert.assertThat(humans.get(0), equalTo(new Human("Jack", 12)));
+    }
+
+    @Test
+    public final void whenSortingEntitiesByNameThenAge_thenCorrectlySorted() {
+        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 12), new Human("Sarah", 10), new Human("Zack", 12));
+        Collections.sort(humans, (lhs, rhs) -> {
+            if (lhs.getName().equals(rhs.getName())) {
+                return lhs.getAge() - rhs.getAge();
+            } else {
+                return lhs.getName().compareTo(rhs.getName());
+            }
+        });
         Assert.assertThat(humans.get(0), equalTo(new Human("Sarah", 10)));
     }
 
+    @Test
+    public final void givenComposition_whenSortingEntitiesByNameThenAge_thenCorrectlySorted() {
+        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 12), new Human("Sarah", 10), new Human("Zack", 12));
+        final Comparator<Human> byName = (h1, h2) -> h1.getName().compareTo(h2.getName());
+        final Comparator<Human> byAge = (h1, h2) -> Ints.compare(h1.getAge(), h2.getAge());
+        Collections.sort(humans, byName.thenComparing(byAge));
+        Assert.assertThat(humans.get(0), equalTo(new Human("Sarah", 10)));
+    }
+
+    @Test
+    public final void whenSortingEntitiesByAge_thenCorrectlySorted() {
+        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
+        Collections.sort(humans, (h1, h2) -> Ints.compare(h1.getAge(), h2.getAge()));
+        Assert.assertThat(humans.get(0), equalTo(new Human("Sarah", 10)));
+    }
+
+    @Test
+    public final void whenSortingEntitiesByNameReversed_thenCorrectlySorted() {
+        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
+        final Comparator<Human> comparator = (h1, h2) -> h1.getName().compareTo(h2.getName());
+        Collections.sort(humans, comparator.reversed());
+        Assert.assertThat(humans.get(0), equalTo(new Human("Sarah", 10)));
+    }
+
+    @Test
+    public final void givenMethodDefinition_whenSortingEntitiesByNameThenAge_thenCorrectlySorted() {
+        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
+        Collections.sort(humans, Human::compareByNameThenAge);
+        Assert.assertThat(humans.get(0), equalTo(new Human("Jack", 12)));
+    }
+
+    @Test
+    public final void givenInstanceMethod_whenSortingEntitiesByName_thenCorrectlySorted() {
+        final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
+        Collections.sort(humans, Comparator.comparing(Human::getName));
+        Assert.assertThat(humans.get(0), equalTo(new Human("Jack", 12)));
+    }
+
 }

core-java-8/src/test/java/org/baeldung/java8/entity/Human.java

@@ -33,6 +33,16 @@ public class Human {
         this.age = age;
     }
 
+    // compare
+
+    public static int compareByNameThenAge(final Human lhs, final Human rhs) {
+        if (lhs.name.equals(rhs.name)) {
+            return lhs.age - rhs.age;
+        } else {
+            return lhs.name.compareTo(rhs.name);
+        }
+    }
+
     //
 
     @Override