[stream-2maap-dup-keys] Handle Duplicated Keys When Producing Map Usi… (#13546)
* [stream-2maap-dup-keys] Handle Duplicated Keys When Producing Map Using Java Streamt * [stream-2maap-dup-keys] create the *-streams-maps module * [stream-2maap-dup-keys] add the new moudle to the parent pom
This commit is contained in:
Kai Yuan
GitHub
parent
7be831c312
commit
0f8f3e0444
|
|
@ -0,0 +1 @@
|
|||
## Relevant Articles:
|
||||
|
|
@ -0,0 +1,67 @@
|
|||
<?xml version="1.0" encoding="UTF-8"?>
|
||||
<project xmlns="http://maven.apache.org/POM/4.0.0"
|
||||
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
|
||||
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
|
||||
<modelVersion>4.0.0</modelVersion>
|
||||
<artifactId>core-java-streams-maps</artifactId>
|
||||
<version>0.1.0-SNAPSHOT</version>
|
||||
<name>core-java-streams-maps</name>
|
||||
<packaging>jar</packaging>
|
||||
|
||||
<parent>
|
||||
<groupId>com.baeldung.core-java-modules</groupId>
|
||||
<artifactId>core-java-modules</artifactId>
|
||||
<version>0.0.1-SNAPSHOT</version>
|
||||
</parent>
|
||||
|
||||
<dependencies>
|
||||
<dependency>
|
||||
<groupId>log4j</groupId>
|
||||
<artifactId>log4j</artifactId>
|
||||
<version>${log4j.version}</version>
|
||||
</dependency>
|
||||
<dependency>
|
||||
<groupId>org.junit</groupId>
|
||||
<artifactId>junit-bom</artifactId>
|
||||
<version>${junit-jupiter.version}</version>
|
||||
<type>pom</type>
|
||||
<scope>import</scope>
|
||||
</dependency>
|
||||
<dependency>
|
||||
<groupId>org.assertj</groupId>
|
||||
<artifactId>assertj-core</artifactId>
|
||||
<version>3.23.1</version>
|
||||
<scope>test</scope>
|
||||
</dependency>
|
||||
</dependencies>
|
||||
|
||||
<build>
|
||||
<finalName>core-java-streams-maps</finalName>
|
||||
<resources>
|
||||
<resource>
|
||||
<directory>src/main</directory>
|
||||
<filtering>true</filtering>
|
||||
</resource>
|
||||
</resources>
|
||||
<plugins>
|
||||
<plugin>
|
||||
<groupId>org.apache.maven.plugins</groupId>
|
||||
<artifactId>maven-compiler-plugin</artifactId>
|
||||
<version>${maven-compiler-plugin.version}</version>
|
||||
<configuration>
|
||||
<source>${maven.compiler.source}</source>
|
||||
<target>${maven.compiler.target}</target>
|
||||
<compilerArgument>-parameters</compilerArgument>
|
||||
</configuration>
|
||||
</plugin>
|
||||
</plugins>
|
||||
</build>
|
||||
|
||||
<properties>
|
||||
<!-- testing -->
|
||||
<maven-compiler-plugin.version>3.1</maven-compiler-plugin.version>
|
||||
<maven.compiler.source>1.8</maven.compiler.source>
|
||||
<maven.compiler.target>1.8</maven.compiler.target>
|
||||
</properties>
|
||||
|
||||
</project>
|
||||
|
|
@ -0,0 +1,97 @@
|
|||
package com.baeldung.streams.tomap;
|
||||
|
||||
import static java.util.stream.Collectors.groupingBy;
|
||||
import static java.util.stream.Collectors.toMap;
|
||||
import static org.junit.jupiter.api.Assertions.assertEquals;
|
||||
|
||||
import java.util.Arrays;
|
||||
import java.util.List;
|
||||
import java.util.Map;
|
||||
import java.util.function.Function;
|
||||
|
||||
import org.junit.jupiter.api.Test;
|
||||
|
||||
class City {
|
||||
private String name;
|
||||
private String locatedIn;
|
||||
|
||||
public City(String name, String locatedIn) {
|
||||
this.name = name;
|
||||
this.locatedIn = locatedIn;
|
||||
}
|
||||
|
||||
public String getName() {
|
||||
return name;
|
||||
}
|
||||
|
||||
public String getLocatedIn() {
|
||||
return locatedIn;
|
||||
}
|
||||
|
||||
@Override
|
||||
public boolean equals(Object o) {
|
||||
if (this == o)
|
||||
return true;
|
||||
if (!(o instanceof City))
|
||||
return false;
|
||||
|
||||
City city = (City) o;
|
||||
|
||||
if (!name.equals(city.name))
|
||||
return false;
|
||||
return locatedIn.equals(city.locatedIn);
|
||||
}
|
||||
|
||||
@Override
|
||||
public int hashCode() {
|
||||
int result = name.hashCode();
|
||||
result = 31 * result + locatedIn.hashCode();
|
||||
return result;
|
||||
}
|
||||
}
|
||||
|
||||
public class StreamToMapDuplicatedKeysHandlingUnitTest {
|
||||
// @formatter:off
|
||||
private final List<City> CITY_INPUT = Arrays.asList(
|
||||
new City("New York City", "USA"),
|
||||
new City("Shanghai", "China"),
|
||||
new City("Hamburg", "Germany"),
|
||||
new City("Paris", "France"),
|
||||
new City("Paris", "Texas, USA"));
|
||||
// @formatter:on
|
||||
|
||||
@Test
|
||||
void givenCityList_whenUsingGroupingBy_shouldContainExpectedCity() {
|
||||
Map<String, List<City>> resultMap = CITY_INPUT.stream()
|
||||
.collect(groupingBy(City::getName));
|
||||
assertEquals(4, resultMap.size());
|
||||
// @formatter:off
|
||||
assertEquals(Arrays.asList(
|
||||
new City("Paris", "France"),
|
||||
new City("Paris", "Texas, USA")), resultMap.get("Paris"));
|
||||
// @formatter:on
|
||||
|
||||
}
|
||||
|
||||
@Test
|
||||
void givenCityList_whenContainingDuplicatedNamesUsingToMap_shouldContainExpectedCity() {
|
||||
Map<String, City> resultMap1 = CITY_INPUT.stream()
|
||||
.collect(toMap(City::getName, Function.identity(), (first, second) -> first));
|
||||
assertEquals(4, resultMap1.size());
|
||||
assertEquals(new City("Paris", "France"), resultMap1.get("Paris"));
|
||||
|
||||
Map<String, City> resultMap2 = CITY_INPUT.stream()
|
||||
.collect(toMap(City::getName, Function.identity(), (first, second) -> second));
|
||||
assertEquals(4, resultMap2.size());
|
||||
assertEquals(new City("Paris", "Texas, USA"), resultMap2.get("Paris"));
|
||||
|
||||
Map<String, City> resultMap3 = CITY_INPUT.stream()
|
||||
.collect(toMap(City::getName, Function.identity(), (first, second) -> {
|
||||
String locations = first.getLocatedIn() + " and " + second.getLocatedIn();
|
||||
return new City(first.getName(), locations);
|
||||
}));
|
||||
assertEquals(4, resultMap2.size());
|
||||
assertEquals(new City("Paris", "France and Texas, USA"), resultMap3.get("Paris"));
|
||||
}
|
||||
|
||||
}
|
||||
|
|
@ -120,6 +120,7 @@
|
|||
<module>core-java-streams</module>
|
||||
<module>core-java-streams-2</module>
|
||||
<module>core-java-streams-3</module>
|
||||
<module>core-java-streams-maps</module>
|
||||
<module>core-java-string-algorithms</module>
|
||||
<module>core-java-string-algorithms-2</module>
|
||||
<module>core-java-string-apis</module>
|
||||
|
|
|
|||
Loading…
Reference in New Issue