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Merge pull request #8992 from alimate/BAEL-3922

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BAEL-3922: Introducing nullsFirst and nullsLast
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Eric Martin 2020-04-01 21:11:03 -05:00 committed by GitHub
commit 18eb5188ca
1 changed files with 53 additions and 10 deletions
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63
core-java-modules/core-java-lambdas/src/test/java/com/baeldung/java8/Java8SortUnitTest.java
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@ -1,18 +1,17 @@
package com.baeldung.java8; package com.baeldung.java8;
import static org.hamcrest.Matchers.equalTo; import com.baeldung.java8.entity.Human;
import com.google.common.collect.Lists;
import com.google.common.primitives.Ints;
import org.junit.Assert;
import org.junit.Test;
import java.util.Collections; import java.util.Collections;
import java.util.Comparator; import java.util.Comparator;
import java.util.List; import java.util.List;
import java.util.stream.Collectors; import java.util.stream.Collectors;
import org.junit.Assert; import static org.hamcrest.Matchers.equalTo;
import org.junit.Test;
import com.baeldung.java8.entity.Human;
import com.google.common.collect.Lists;
import com.google.common.primitives.Ints;
public class Java8SortUnitTest { public class Java8SortUnitTest {
@ -113,11 +112,11 @@ public class Java8SortUnitTest {
humans.sort(Comparator.comparing(Human::getName)); humans.sort(Comparator.comparing(Human::getName));
Assert.assertThat(humans.get(0), equalTo(new Human("Jack", 12))); Assert.assertThat(humans.get(0), equalTo(new Human("Jack", 12)));
} }
@Test @Test
public final void givenStreamNaturalOrdering_whenSortingEntitiesByName_thenCorrectlySorted() { public final void givenStreamNaturalOrdering_whenSortingEntitiesByName_thenCorrectlySorted() {
final List<String> letters = Lists.newArrayList("B", "A", "C"); final List<String> letters = Lists.newArrayList("B", "A", "C");
final List<String> sortedLetters = letters.stream().sorted().collect(Collectors.toList()); final List<String> sortedLetters = letters.stream().sorted().collect(Collectors.toList());
Assert.assertThat(sortedLetters.get(0), equalTo("A")); Assert.assertThat(sortedLetters.get(0), equalTo("A"));
} }
@ -126,7 +125,7 @@ public class Java8SortUnitTest {
public final void givenStreamCustomOrdering_whenSortingEntitiesByName_thenCorrectlySorted() { public final void givenStreamCustomOrdering_whenSortingEntitiesByName_thenCorrectlySorted() {
final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12)); final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
final Comparator<Human> nameComparator = (h1, h2) -> h1.getName().compareTo(h2.getName()); final Comparator<Human> nameComparator = (h1, h2) -> h1.getName().compareTo(h2.getName());
final List<Human> sortedHumans = humans.stream().sorted(nameComparator).collect(Collectors.toList()); final List<Human> sortedHumans = humans.stream().sorted(nameComparator).collect(Collectors.toList());
Assert.assertThat(sortedHumans.get(0), equalTo(new Human("Jack", 12))); Assert.assertThat(sortedHumans.get(0), equalTo(new Human("Jack", 12)));
} }
@ -164,4 +163,48 @@ public class Java8SortUnitTest {
Assert.assertThat(reverseSortedHumans.get(0), equalTo(new Human("Sarah", 10))); Assert.assertThat(reverseSortedHumans.get(0), equalTo(new Human("Sarah", 10)));
} }
@Test(expected = NullPointerException.class)
public final void givenANullElement_whenSortingEntitiesByName_thenThrowsNPE() {
final List<Human> humans = Lists.newArrayList(null, new Human("Jack", 12));
humans.sort((h1, h2) -> h1.getName().compareTo(h2.getName()));
}
@Test
public final void givenANullElement_whenSortingEntitiesByNameManually_thenMovesTheNullToLast() {
final List<Human> humans = Lists.newArrayList(null, new Human("Jack", 12), null);
humans.sort((h1, h2) -> {
if (h1 == null) return h2 == null ? 0 : 1;
else if (h2 == null) return -1;
return h1.getName().compareTo(h2.getName());
});
Assert.assertNotNull(humans.get(0));
Assert.assertNull(humans.get(1));
Assert.assertNull(humans.get(2));
}
@Test
public final void givenANullElement_whenSortingEntitiesByName_thenMovesTheNullToLast() {
final List<Human> humans = Lists.newArrayList(null, new Human("Jack", 12), null);
humans.sort(Comparator.nullsLast(Comparator.comparing(Human::getName)));
Assert.assertNotNull(humans.get(0));
Assert.assertNull(humans.get(1));
Assert.assertNull(humans.get(2));
}
@Test
public final void givenANullElement_whenSortingEntitiesByName_thenMovesTheNullToStart() {
final List<Human> humans = Lists.newArrayList(null, new Human("Jack", 12), null);
humans.sort(Comparator.nullsFirst(Comparator.comparing(Human::getName)));
Assert.assertNull(humans.get(0));
Assert.assertNull(humans.get(1));
Assert.assertNotNull(humans.get(2));
}
} }