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

This commit is contained in:
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;
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.assertThrows;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import org.junit.jupiter.api.Test;
import com.google.common.collect.Lists;
public class MapStreamToMapUnitTest {
Map<String, Integer> playerMap1 = new HashMap<String, Integer>() {{
@ -36,12 +36,6 @@ public class MapStreamToMapUnitTest {
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
void givenMapsStream_whenUsingFlatMapAndToMap_thenMultipleMapsMergedIntoOneMap() {
@ -53,7 +47,8 @@ public class MapStreamToMapUnitTest {
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())
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
@ -71,11 +66,13 @@ public class MapStreamToMapUnitTest {
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())
.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())
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, Integer::max));
@ -104,12 +101,14 @@ public class MapStreamToMapUnitTest {
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())
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, Integer::max)));
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())
.forEach(entry -> {
String k = entry.getKey();
@ -135,19 +134,10 @@ public class MapStreamToMapUnitTest {
put("Kevin", 77);
put("Jerry", null);
}};
Stream<Map<String, Integer>> mapStream = getMapStream(playerMap1, playerMap2, playerMap3, playerMap4, playerMap5);
Map<String, Integer> mergedMap = mapStream.reduce(new HashMap<>(), (resultMap, theMap) -> {
theMap.forEach((k, v) -> {
if (resultMap.containsKey(k)) {
resultMap.put(k, maxInteger(resultMap.get(k), v));
} else {
resultMap.put(k, v);
}
});
return resultMap;
});
Map<String, Integer> mergedMap = Stream.of(playerMap1, playerMap2, playerMap3, playerMap4, playerMap5)
.flatMap(x -> x.entrySet()
.stream())
.collect(groupingBy(Map.Entry::getKey, mapping(Map.Entry::getValue, reducing(null, this::maxInteger))));
assertEquals(expectedMap, mergedMap);
}
}