Add complete codes for an article about deep copy (#3610)
* Add complete codes for an article about deep copy * Add missing gson dependency * Apply changes suggested in PR comments * Apply changes suggested in PR comments * Apply changes suggested in PR comments
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xenteros
KevinGilmore
parent
378cae0821
commit
327719e1bb
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@ -78,6 +78,11 @@
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<artifactId>jackson-databind</artifactId>
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<version>${jackson.version}</version>
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</dependency>
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<dependency>
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<groupId>com.google.code.gson</groupId>
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<artifactId>gson</artifactId>
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<version>${gson.version}</version>
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</dependency>
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<!-- logging -->
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<dependency>
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@ -468,6 +473,7 @@
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<properties>
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<!-- marshalling -->
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<jackson.version>2.8.5</jackson.version>
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<gson.version>2.8.2</gson.version>
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<!-- logging -->
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<org.slf4j.version>1.7.21</org.slf4j.version>
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@ -0,0 +1,59 @@
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package com.baeldung.deepcopy;
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import java.io.Serializable;
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public class Address implements Serializable, Cloneable {
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@Override
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public Object clone() {
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try {
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return (Address) super.clone();
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} catch (CloneNotSupportedException e) {
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return new Address(this.street, this.getCity(), this.getCountry());
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}
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}
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private static final long serialVersionUID = 1740913841244949416L;
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private String street;
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private String city;
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private String country;
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public Address(Address that) {
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this(that.getStreet(), that.getCity(), that.getCountry());
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}
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public Address(String street, String city, String country) {
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this.street = street;
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this.city = city;
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this.country = country;
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}
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public Address() {
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}
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public String getStreet() {
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return street;
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}
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public String getCity() {
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return city;
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}
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public String getCountry() {
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return country;
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}
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public void setStreet(String street) {
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this.street = street;
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}
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public void setCity(String city) {
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this.city = city;
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}
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public void setCountry(String country) {
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this.country = country;
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}
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}
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@ -0,0 +1,48 @@
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package com.baeldung.deepcopy;
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import java.io.Serializable;
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public class User implements Serializable, Cloneable {
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private static final long serialVersionUID = -3427002229954777557L;
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private String firstName;
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private String lastName;
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private Address address;
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public User(String firstName, String lastName, Address address) {
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this.firstName = firstName;
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this.lastName = lastName;
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this.address = address;
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}
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public User(User that) {
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this(that.getFirstName(), that.getLastName(), new Address(that.getAddress()));
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}
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public User() {
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}
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@Override
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public Object clone() {
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User user;
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try {
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user = (User) super.clone();
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} catch (CloneNotSupportedException e) {
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user = new User(this.getFirstName(), this.getLastName(), this.getAddress());
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}
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user.address = (Address) this.address.clone();
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return user;
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}
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public String getFirstName() {
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return firstName;
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}
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public String getLastName() {
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return lastName;
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}
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public Address getAddress() {
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return address;
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}
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}
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@ -0,0 +1,128 @@
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package com.baeldung.deepcopy;
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import static org.assertj.core.api.Assertions.assertThat;
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import java.io.IOException;
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import org.apache.commons.lang.SerializationUtils;
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import org.junit.Ignore;
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import org.junit.Test;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import com.google.gson.Gson;
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public class DeepCopyUnitTest {
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@Test
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public void whenCreatingDeepCopyWithCopyConstructor_thenObjectsShouldNotBeSame() {
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Address address = new Address("Downing St 10", "London", "England");
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User pm = new User("Prime", "Minister", address);
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User deepCopy = new User(pm);
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assertThat(deepCopy).isNotSameAs(pm);
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}
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@Test
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public void whenModifyingOriginalObject_thenConstructorCopyShouldNotChange() {
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Address address = new Address("Downing St 10", "London", "England");
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User pm = new User("Prime", "Minister", address);
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User deepCopy = new User(pm);
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address.setCountry("Great Britain");
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assertThat(deepCopy.getAddress().getCountry()).isNotEqualTo(pm.getAddress().getCountry());
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}
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@Test
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public void whenModifyingOriginalObject_thenCloneCopyShouldNotChange() {
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Address address = new Address("Downing St 10", "London", "England");
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User pm = new User("Prime", "Minister", address);
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User deepCopy = (User) pm.clone();
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address.setCountry("Great Britain");
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assertThat(deepCopy.getAddress().getCountry()).isNotEqualTo(pm.getAddress().getCountry());
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}
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@Test
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public void whenModifyingOriginalObject_thenCommonsCloneShouldNotChange() {
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Address address = new Address("Downing St 10", "London", "England");
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User pm = new User("Prime", "Minister", address);
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User deepCopy = (User) SerializationUtils.clone(pm);
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address.setCountry("Great Britain");
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assertThat(deepCopy.getAddress().getCountry()).isNotEqualTo(pm.getAddress().getCountry());
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}
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@Test
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public void whenModifyingOriginalObject_thenGsonCloneShouldNotChange() {
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Address address = new Address("Downing St 10", "London", "England");
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User pm = new User("Prime", "Minister", address);
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Gson gson = new Gson();
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User deepCopy = gson.fromJson(gson.toJson(pm), User.class);
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address.setCountry("Great Britain");
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assertThat(deepCopy.getAddress().getCountry()).isNotEqualTo(pm.getAddress().getCountry());
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}
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@Test
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public void whenModifyingOriginalObject_thenJacksonCopyShouldNotChange() throws IOException {
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Address address = new Address("Downing St 10", "London", "England");
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User pm = new User("Prime", "Minister", address);
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ObjectMapper objectMapper = new ObjectMapper();
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User deepCopy = objectMapper.readValue(objectMapper.writeValueAsString(pm), User.class);
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address.setCountry("Great Britain");
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assertThat(deepCopy.getAddress().getCountry()).isNotEqualTo(pm.getAddress().getCountry());
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}
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@Test
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@Ignore
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public void whenMakingCopies_thenShowHowLongEachMethodTakes() throws CloneNotSupportedException, IOException {
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int times = 1000000;
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Address address = new Address("Downing St 10", "London", "England");
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User pm = new User("Prime", "Minister", address);
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long start = System.currentTimeMillis();
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for (int i = 0; i < times; i++) {
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User primeMinisterClone = (User) SerializationUtils.clone(pm);
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}
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long end = System.currentTimeMillis();
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System.out.println("Cloning with Apache Commons Lang took " + (end - start) + " milliseconds.");
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start = System.currentTimeMillis();
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Gson gson = new Gson();
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for (int i = 0; i < times; i++) {
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User primeMinisterClone = gson.fromJson(gson.toJson(pm), User.class);
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}
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end = System.currentTimeMillis();
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System.out.println("Cloning with Gson took " + (end - start) + " milliseconds.");
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start = System.currentTimeMillis();
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for (int i = 0; i < times; i++) {
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User primeMinisterClone = new User(pm);
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}
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end = System.currentTimeMillis();
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System.out.println("Cloning with the copy constructor took " + (end - start) + " milliseconds.");
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start = System.currentTimeMillis();
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for (int i = 0; i < times; i++) {
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User primeMinisterClone = (User) pm.clone();
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}
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end = System.currentTimeMillis();
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System.out.println("Cloning with Cloneable interface took " + (end - start) + " milliseconds.");
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start = System.currentTimeMillis();
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ObjectMapper objectMapper = new ObjectMapper();
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for (int i = 0; i < times; i++) {
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User primeMinisterClone = objectMapper.readValue(objectMapper.writeValueAsString(pm), User.class);
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}
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end = System.currentTimeMillis();
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System.out.println("Cloning with Jackson took " + (end - start) + " milliseconds.");
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}
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}
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@ -0,0 +1,33 @@
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package com.baeldung.deepcopy;
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import static org.assertj.core.api.Assertions.assertThat;
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import org.junit.Test;
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public class ShallowCopyUnitTest {
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@Test
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public void whenShallowCopying_thenObjectsShouldNotBeSame() {
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Address address = new Address("Downing St 10", "London", "England");
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User pm = new User("Prime", "Minister", address);
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User shallowCopy = new User(pm.getFirstName(), pm.getLastName(), pm.getAddress());
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assertThat(shallowCopy)
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.isNotSameAs(pm);
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}
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@Test
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public void whenModifyingOriginalObject_thenCopyShouldChange() {
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Address address = new Address("Downing St 10", "London", "England");
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User pm = new User("Prime", "Minister", address);
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User shallowCopy = new User(pm.getFirstName(), pm.getLastName(), pm.getAddress());
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address.setCountry("Great Britain");
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assertThat(shallowCopy.getAddress().getCountry())
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.isEqualTo(pm.getAddress().getCountry());
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}
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}
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