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* Added examples for java-9 filtering collector

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geroza 2018-07-25 11:41:51 -03:00 committed by José Carlos Valero Sánchez
parent 5b489423d8
commit 6b2fb615a7
3 changed files with 94 additions and 0 deletions
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14
core-java-9/pom.xml
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@ -19,11 +19,23 @@
<version>${awaitility.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>${assertj.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>${guava.version}</version>
</dependency>
<dependency>
<groupId>org.junit.platform</groupId>
<artifactId>junit-platform-runner</artifactId>
<version>${junit.platform.version}</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
@ -50,6 +62,8 @@
<properties>
<!-- testing -->
<assertj.version>3.10.0</assertj.version>
<junit.platform.version>1.2.0</junit.platform.version>
<awaitility.version>1.7.0</awaitility.version>
<maven.compiler.source>1.9</maven.compiler.source>
<maven.compiler.target>1.9</maven.compiler.target>

27
core-java-9/src/main/java/com/baeldung/java9/language/stream/StreamsGroupingCollectionFilter.java Normal file
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@ -0,0 +1,27 @@
package com.baeldung.java9.language.stream;
import static java.util.stream.Collectors.filtering;
import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.toList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
public class StreamsGroupingCollectionFilter {
static public Map<Integer, List<Integer>> findEvenNumbersAfterGroupingByQuantityOfDigits(Collection<Integer> baseCollection) {
Function<Integer, Integer> getQuantityOfDigits = item -> (int) Math.log10(item) + 1;
return baseCollection.stream()
.collect(groupingBy(getQuantityOfDigits, filtering(item -> item % 2 == 0, toList())));
}
static public Map<Integer, List<Integer>> findEvenNumbersBeforeGroupingByQuantityOfDigits(Collection<Integer> baseCollection) {
return baseCollection.stream()
.filter(item -> item % 2 == 0)
.collect(groupingBy(item -> (int) Math.log10(item) + 1, toList()));
}
}

53
core-java-9/src/test/java/com/baeldung/java9/language/stream/CollectionFilterUnitTest.java Normal file
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@ -0,0 +1,53 @@
package com.baeldung.java9.language.stream;
import static org.assertj.core.api.Assertions.assertThat;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.junit.jupiter.api.Test;
import org.junit.platform.runner.JUnitPlatform;
import org.junit.runner.RunWith;
@RunWith(JUnitPlatform.class)
public class CollectionFilterUnitTest {
private static final Collection<Integer> BASE_INTEGER_COLLECTION = Arrays.asList(9, 12, 55, 56, 101, 115, 8002, 223, 2668, 19, 8);
private static final Map<Integer, List<Integer>> EXPECTED_EVEN_FILTERED_AFTER_GROUPING_MAP = createExpectedFilterAfterGroupingMap();
private static Map<Integer, List<Integer>> createExpectedFilterAfterGroupingMap() {
Map<Integer, List<Integer>> map = new HashMap<>();
map.put(1, Arrays.asList(8));
map.put(2, Arrays.asList(12, 56));
map.put(3, Collections.emptyList());
map.put(4, Arrays.asList(8002, 2668));
return map;
}
private static final Map<Integer, List<Integer>> EXPECTED_EVEN_FILTERED_BEFORE_GROUPING_MAP = createExpectedFilterBeforeGroupingMap();
private static Map<Integer, List<Integer>> createExpectedFilterBeforeGroupingMap() {
Map<Integer, List<Integer>> map = new HashMap<>();
map.put(1, Arrays.asList(8));
map.put(2, Arrays.asList(12, 56));
map.put(4, Arrays.asList(8002, 2668));
return map;
}
@Test
public void givenAStringCollection_whenFilteringFourLetterWords_thenObtainTheFilteredCollection() {
Map<Integer, List<Integer>> filteredAfterGroupingMap = StreamsGroupingCollectionFilter.findEvenNumbersAfterGroupingByQuantityOfDigits(BASE_INTEGER_COLLECTION);
Map<Integer, List<Integer>> filteredBeforeGroupingMap = StreamsGroupingCollectionFilter.findEvenNumbersBeforeGroupingByQuantityOfDigits(BASE_INTEGER_COLLECTION);
assertThat(filteredAfterGroupingMap).containsAllEntriesOf(EXPECTED_EVEN_FILTERED_AFTER_GROUPING_MAP);
assertThat(filteredBeforeGroupingMap).doesNotContainKey(3)
.containsAllEntriesOf(EXPECTED_EVEN_FILTERED_BEFORE_GROUPING_MAP);
}
}