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Java 8 sort objects
/*
src: https://github.com/kwoyke/tutorials/blob/e398e2bae02c8991867bbc38dad9171013d8299b/core-java-8/src/test/java/com/baeldung/java8/Java8SortUnitTest.java
*/
import static org.hamcrest.Matchers.equalTo;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import org.junit.Assert;
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 {
// 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));
humans.sort((final Human h1, final Human h2) -> h1.getName().compareTo(h2.getName()));
Assert.assertThat(humans.get(0), equalTo(new Human("Jack", 12)));
}
@Test
public final void givenLambdaShortForm_whenSortingEntitiesByName_thenCorrectlySorted() {
final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
humans.sort((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));
humans.sort((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 givenCompositionVerbose_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());
humans.sort(byName.thenComparing(byAge));
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));
humans.sort(Comparator.comparing(Human::getName).thenComparing(Human::getAge));
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));
humans.sort((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());
humans.sort(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));
humans.sort(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));
humans.sort(Comparator.comparing(Human::getName));
Assert.assertThat(humans.get(0), equalTo(new Human("Jack", 12)));
}
@Test
public final void givenStreamNaturalOrdering_whenSortingEntitiesByName_thenCorrectlySorted() {
final List<String> letters = Lists.newArrayList("B", "A", "C");
final List<String> sortedLetters = letters.stream().sorted().collect(Collectors.toList());
Assert.assertThat(sortedLetters.get(0), equalTo("A"));
}
@Test
public final void givenStreamCustomOrdering_whenSortingEntitiesByName_thenCorrectlySorted() {
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 List<Human> sortedHumans = humans.stream().sorted(nameComparator).collect(Collectors.toList());
Assert.assertThat(sortedHumans.get(0), equalTo(new Human("Jack", 12)));
}
@Test
public final void givenStreamComparatorOrdering_whenSortingEntitiesByName_thenCorrectlySorted() {
final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
final List<Human> sortedHumans = humans.stream().sorted(Comparator.comparing(Human::getName)).collect(Collectors.toList());
Assert.assertThat(sortedHumans.get(0), equalTo(new Human("Jack", 12)));
}
@Test
public final void givenStreamNaturalOrdering_whenSortingEntitiesByNameReversed_thenCorrectlySorted() {
final List<String> letters = Lists.newArrayList("B", "A", "C");
final List<String> reverseSortedLetters = letters.stream().sorted(Comparator.reverseOrder()).collect(Collectors.toList());
Assert.assertThat(reverseSortedLetters.get(0), equalTo("C"));
}
@Test
public final void givenStreamCustomOrdering_whenSortingEntitiesByNameReversed_thenCorrectlySorted() {
final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
final Comparator<Human> reverseNameComparator = (h1, h2) -> h2.getName().compareTo(h1.getName());
final List<Human> reverseSortedHumans = humans.stream().sorted(reverseNameComparator).collect(Collectors.toList());
Assert.assertThat(reverseSortedHumans.get(0), equalTo(new Human("Sarah", 10)));
}
@Test
public final void givenStreamComparatorOrdering_whenSortingEntitiesByNameReversed_thenCorrectlySorted() {
final List<Human> humans = Lists.newArrayList(new Human("Sarah", 10), new Human("Jack", 12));
final List<Human> reverseSortedHumans = humans.stream().sorted(Comparator.comparing(Human::getName, Comparator.reverseOrder())).collect(Collectors.toList());
Assert.assertThat(reverseSortedHumans.get(0), equalTo(new Human("Sarah", 10)));
}
}
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