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Merge pull request #6652 from SmartyAnsh/master 

BAEL-2800 -  BAEL-2800_Copying_a_HashMap_in_Java - new module added
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Eric Martin 2019-04-11 22:12:25 -05:00 committed by GitHub
parent 759bcd045b 437efd7242
commit 9ff896fe4e
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6
core-java-collections-map/README.md Normal file
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=========
## Core Java Collections 2
### Relevant Articles:
- Java - Copying a HashMap

78
core-java-collections-map/pom.xml Normal file
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<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-collections-map</artifactId>
<version>0.1.0-SNAPSHOT</version>
<name>core-java-collections-map</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung</groupId>
<artifactId>parent-java</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../parent-java</relativePath>
</parent>
<dependencies>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-collections4</artifactId>
<version>${commons-collections4.version}</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>${commons-lang3.version}</version>
</dependency>
<dependency>
<groupId>org.eclipse.collections</groupId>
<artifactId>eclipse-collections</artifactId>
<version>${eclipse.collections.version}</version>
</dependency>
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>${assertj.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.junit.platform</groupId>
<artifactId>junit-platform-runner</artifactId>
<version>${junit.platform.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-core</artifactId>
<version>${openjdk.jmh.version}</version>
</dependency>
<dependency>
<groupId>org.openjdk.jmh</groupId>
<artifactId>jmh-generator-annprocess</artifactId>
<version>${openjdk.jmh.version}</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-exec</artifactId>
<version>${commons-exec.version}</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>${lombok.version}</version>
<scope>provided</scope>
</dependency>
</dependencies>
<properties>
<openjdk.jmh.version>1.19</openjdk.jmh.version>
<junit.platform.version>1.2.0</junit.platform.version>
<commons-lang3.version>3.8.1</commons-lang3.version>
<commons-collections4.version>4.1</commons-collections4.version>
<collections-generic.version>4.01</collections-generic.version>
<avaitility.version>1.7.0</avaitility.version>
<assertj.version>3.11.1</assertj.version>
<eclipse.collections.version>7.1.0</eclipse.collections.version>
<commons-exec.version>1.3</commons-exec.version>
</properties>
</project>

55
core-java-collections-map/src/main/java/com/baeldung/copyinghashmap/CopyHashMap.java Normal file
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package com.baeldung.copyinghashmap;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.stream.Collectors;
import org.apache.commons.lang3.SerializationUtils;
public class CopyHashMap {
public static <String, Employee> HashMap<String, Employee> copyUsingConstructor(HashMap<String, Employee> originalMap) {
return new HashMap<String, Employee>(originalMap);
}
public static <String, Employee> HashMap<String, Employee> copyUsingClone(HashMap<String, Employee> originalMap) {
return (HashMap<String, Employee>) originalMap.clone();
}
public static <String, Employee> HashMap<String, Employee> copyUsingPut(HashMap<String, Employee> originalMap) {
HashMap<String, Employee> shallowCopy = new HashMap<String, Employee>();
Set<Entry<String, Employee>> entries = originalMap.entrySet();
for(Map.Entry<String, Employee> mapEntry: entries) {
shallowCopy.put(mapEntry.getKey(), mapEntry.getValue());
}
return shallowCopy;
}
public static <String, Employee> HashMap<String, Employee> copyUsingPutAll(HashMap<String, Employee> originalMap) {
HashMap<String, Employee> shallowCopy = new HashMap<String, Employee>();
shallowCopy.putAll(originalMap);
return shallowCopy;
}
public static <String, Employee> HashMap<String, Employee> copyUsingJava8Stream(HashMap<String, Employee> originalMap) {
Set<Entry<String, Employee>> entries = originalMap.entrySet();
HashMap<String, Employee> shallowCopy = (HashMap<String, Employee>) entries
.stream()
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
return shallowCopy;
}
public static <String, Employee> HashMap<String, Employee> shallowCopy(HashMap<String, Employee> originalMap) {
return (HashMap<String, Employee>) originalMap.clone();
}
public static <String, Employee> HashMap<String, Employee> deepCopy(HashMap<String, Employee> originalMap) {
return SerializationUtils.clone(originalMap);
}
}

77
core-java-collections-map/src/test/java/com/baeldung/copyinghashmap/CopyHashMapUnitTest.java Normal file
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package com.baeldung.copyinghashmap;
import static org.assertj.core.api.Assertions.assertThat;
import java.util.HashMap;
import java.util.Map;
import org.junit.Test;
import com.google.common.collect.ImmutableMap;
public class CopyHashMapUnitTest {
@Test
public void givenHashMap_whenShallowCopy_thenCopyisNotSameAsOriginal() {
HashMap<String, Employee> map = new HashMap<>();
Employee emp1 = new Employee("John");
Employee emp2 = new Employee("Norman");
map.put("emp1",emp1);
map.put("emp2",emp2);
HashMap<String, Employee> shallowCopy = CopyHashMap.shallowCopy(map);
assertThat(shallowCopy).isNotSameAs(map);
}
@Test
public void givenHashMap_whenShallowCopyModifyingOriginalObject_thenCopyShouldChange() {
HashMap<String, Employee> map = new HashMap<>();
Employee emp1 = new Employee("John");
Employee emp2 = new Employee("Norman");
map.put("emp1",emp1);
map.put("emp2",emp2);
HashMap<String, Employee> shallowCopy = CopyHashMap.shallowCopy(map);
emp1.setName("Johny");
assertThat(shallowCopy.get("emp1")).isEqualTo(map.get("emp1"));
}
@Test
public void givenHashMap_whenDeepCopyModifyingOriginalObject_thenCopyShouldNotChange() {
HashMap<String, Employee> map = new HashMap<>();
Employee emp1 = new Employee("John");
Employee emp2 = new Employee("Norman");
map.put("emp1",emp1);
map.put("emp2",emp2);
HashMap<String, Employee> deepCopy = CopyHashMap.deepCopy(map);
emp1.setName("Johny");
assertThat(deepCopy.get("emp1")).isNotEqualTo(map.get("emp1"));
}
@Test
public void givenImmutableMap_whenCopyUsingGuava_thenCopyShouldNotChange() {
Employee emp1 = new Employee("John");
Employee emp2 = new Employee("Norman");
Map<String, Employee> map = ImmutableMap.<String, Employee> builder()
.put("emp1",emp1)
.put("emp2",emp2)
.build();
Map<String, Employee> shallowCopy = ImmutableMap.copyOf(map);
assertThat(shallowCopy).isSameAs(map);
}
}

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core-java-collections-map/src/test/java/com/baeldung/copyinghashmap/Employee.java Normal file
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package com.baeldung.copyinghashmap;
import java.io.Serializable;
public class Employee implements Serializable{
private String name;
public Employee(String name) {
super();
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return this.name;
}
}

2
pom.xml
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<!--<module>core-java-os</module> --> <!-- We haven't upgraded to java 9.--> <!--<module>core-java-os</module> --> <!-- We haven't upgraded to java 9.-->
<module>core-java-arrays</module> <module>core-java-arrays</module>
<module>core-java-collections</module> <module>core-java-collections</module>
<module>core-java-collections-map</module>
<module>core-java-collections-list</module> <module>core-java-collections-list</module>
<module>core-java-concurrency-basic</module> <module>core-java-concurrency-basic</module>
<module>core-java-concurrency-collections</module> <module>core-java-concurrency-collections</module>
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<!--<module>core-java-os</module> --> <!-- We haven't upgraded to java 9.--> <!--<module>core-java-os</module> --> <!-- We haven't upgraded to java 9.-->
<module>core-java-arrays</module> <module>core-java-arrays</module>
<module>core-java-collections</module> <module>core-java-collections</module>
<module>core-java-collections-map</module>
<module>core-java-collections-list</module> <module>core-java-collections-list</module>
<module>core-java-concurrency-basic</module> <module>core-java-concurrency-basic</module>
<module>core-java-concurrency-collections</module> <module>core-java-concurrency-collections</module>