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[map-stream-to-map] updates.. 1

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Kai.Yuan 2024-03-19 09:32:58 +01:00
parent 614d910766
commit 9456b4b953
1 changed files with 18 additions and 28 deletions
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46
core-java-modules/core-java-streams-maps/src/test/java/com/baeldung/streams/mapstreamtomap/MapStreamToMapUnitTest.java
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@ -1,20 +1,20 @@
package com.baeldung.streams.mapstreamtomap; package com.baeldung.streams.mapstreamtomap;
import static java.lang.Math.max; import static java.lang.Math.max;
import static java.util.stream.Collectors.flatMapping;
import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.mapping;
import static java.util.stream.Collectors.reducing;
import static org.junit.jupiter.api.Assertions.assertEquals; import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows; import static org.junit.jupiter.api.Assertions.assertThrows;
import java.util.Collections;
import java.util.HashMap; import java.util.HashMap;
import java.util.List;
import java.util.Map; import java.util.Map;
import java.util.stream.Collectors; import java.util.stream.Collectors;
import java.util.stream.Stream; import java.util.stream.Stream;
import org.junit.jupiter.api.Test; import org.junit.jupiter.api.Test;
import com.google.common.collect.Lists;
public class MapStreamToMapUnitTest { public class MapStreamToMapUnitTest {
Map<String, Integer> playerMap1 = new HashMap<String, Integer>() {{ Map<String, Integer> playerMap1 = new HashMap<String, Integer>() {{
@ -36,12 +36,6 @@ public class MapStreamToMapUnitTest {
put("Jerry", null); put("Jerry", null);
}}; }};
static Stream<Map<String, Integer>> getMapStream(Map<String, Integer>... playerMaps) {
List<Map<String, Integer>> theList = Lists.newArrayList(playerMaps);
Collections.shuffle(theList);
return theList.stream();
}
@Test @Test
void givenMapsStream_whenUsingFlatMapAndToMap_thenMultipleMapsMergedIntoOneMap() { void givenMapsStream_whenUsingFlatMapAndToMap_thenMultipleMapsMergedIntoOneMap() {
@ -53,7 +47,8 @@ public class MapStreamToMapUnitTest {
put("Kevin", 77); put("Kevin", 77);
}}; }};
Map<String, Integer> mergedMap = getMapStream(playerMap1, playerMap2, playerMap3).flatMap(map -> map.entrySet() Map<String, Integer> mergedMap = Stream.of(playerMap1, playerMap2, playerMap3)
.flatMap(map -> map.entrySet()
.stream()) .stream())
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue)); .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
@ -71,11 +66,13 @@ public class MapStreamToMapUnitTest {
put("Kevin", 77); put("Kevin", 77);
}}; }};
assertThrows(IllegalStateException.class, () -> getMapStream(playerMap1, playerMap2, playerMap3, playerMap4).flatMap(map -> map.entrySet() assertThrows(IllegalStateException.class, () -> Stream.of(playerMap1, playerMap2, playerMap3, playerMap4)
.flatMap(map -> map.entrySet()
.stream()) .stream())
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue)), "Duplicate key Kai (attempted merging values 92 and 76)"); .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue)), "Duplicate key Kai (attempted merging values 92 and 76)");
Map<String, Integer> mergedMap = getMapStream(playerMap1, playerMap2, playerMap3, playerMap4).flatMap(map -> map.entrySet() Map<String, Integer> mergedMap = Stream.of(playerMap1, playerMap2, playerMap3, playerMap4)
.flatMap(map -> map.entrySet()
.stream()) .stream())
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, Integer::max)); .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, Integer::max));
@ -104,12 +101,14 @@ public class MapStreamToMapUnitTest {
put("Jerry", null); put("Jerry", null);
}}; }};
assertThrows(NullPointerException.class, () -> getMapStream(playerMap1, playerMap2, playerMap3, playerMap4, playerMap5).flatMap(map -> map.entrySet() assertThrows(NullPointerException.class, () -> Stream.of(playerMap1, playerMap2, playerMap3, playerMap4, playerMap5)
.flatMap(map -> map.entrySet()
.stream()) .stream())
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, Integer::max))); .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, Integer::max)));
Map<String, Integer> mergedMap = new HashMap<>(); Map<String, Integer> mergedMap = new HashMap<>();
getMapStream(playerMap1, playerMap2, playerMap3, playerMap4, playerMap5).flatMap(map -> map.entrySet() Stream.of(playerMap1, playerMap2, playerMap3, playerMap4, playerMap5)
.flatMap(map -> map.entrySet()
.stream()) .stream())
.forEach(entry -> { .forEach(entry -> {
String k = entry.getKey(); String k = entry.getKey();
@ -135,19 +134,10 @@ public class MapStreamToMapUnitTest {
put("Kevin", 77); put("Kevin", 77);
put("Jerry", null); put("Jerry", null);
}}; }};
Stream<Map<String, Integer>> mapStream = getMapStream(playerMap1, playerMap2, playerMap3, playerMap4, playerMap5); Map<String, Integer> mergedMap = Stream.of(playerMap1, playerMap2, playerMap3, playerMap4, playerMap5)
Map<String, Integer> mergedMap = mapStream.reduce(new HashMap<>(), (resultMap, theMap) -> { .flatMap(x -> x.entrySet()
theMap.forEach((k, v) -> { .stream())
if (resultMap.containsKey(k)) { .collect(groupingBy(Map.Entry::getKey, mapping(Map.Entry::getValue, reducing(null, this::maxInteger))));
resultMap.put(k, maxInteger(resultMap.get(k), v));
} else {
resultMap.put(k, v);
}
});
return resultMap;
});
assertEquals(expectedMap, mergedMap); assertEquals(expectedMap, mergedMap);
} }
} }