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dupirefr
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[BAEL-3981] Code for article
* Equality operators * Object#equals method * Objects#equals static method * Comparable interface * Comparator interface * Apache Commons features * Guava features
1 parent 4909263 commit d1e64fb

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Lines changed: 791 additions & 1 deletion

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‎core-java-modules/core-java-lang-2/pom.xml‎

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<dependency>
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<groupId>org.apache.commons</groupId>
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<artifactId>commons-lang3</artifactId>
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<version>3.9</version>
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<version>${commons-lang3.version}</version>
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</dependency>
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<dependency>
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<groupId>com.google.guava</groupId>
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<artifactId>guava</artifactId>
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<version>${guava.version}</version>
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</dependency>
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<dependency>
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<groupId>commons-beanutils</groupId>
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<jmh-generator.version>1.19</jmh-generator.version>
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<assertj.version>3.12.2</assertj.version>
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<commons.beanutils.version>1.9.4</commons.beanutils.version>
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<commons-lang3.version>3.9</commons-lang3.version>
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<guava.version>29.0-jre</guava.version>
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</properties>
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</project>

‎core-java-modules/core-java-lang-2/src/main/java/com/baeldung/comparing/Person.java‎

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package com.baeldung.comparing;
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import java.time.LocalDate;
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import java.util.Comparator;
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import java.util.Objects;
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public class Person {
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public static class PersonWithoutEquals {
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private String firstName;
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private String lastName;
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public PersonWithoutEquals(String firstName, String lastName) {
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this.firstName = firstName;
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this.lastName = lastName;
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}
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}
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public static class PersonWithEquals {
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private String firstName;
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private String lastName;
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private LocalDate birthDate;
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public PersonWithEquals(String firstName, String lastName) {
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if (firstName == null || lastName == null) {
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throw new NullPointerException("Names can't be null");
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}
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this.firstName = firstName;
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this.lastName = lastName;
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}
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public PersonWithEquals(String firstName, String lastName, LocalDate birthDate) {
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this(firstName, lastName);
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this.birthDate = birthDate;
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}
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public String firstName() {
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return firstName;
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}
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public String lastName() {
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return lastName;
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}
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public LocalDate birthDate() {
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return birthDate;
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}
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@Override
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public boolean equals(Object o) {
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if (this == o) return true;
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if (o == null || getClass() != o.getClass()) return false;
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PersonWithEquals that = (PersonWithEquals) o;
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return firstName.equals(that.firstName) &&
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lastName.equals(that.lastName) &&
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Objects.equals(birthDate, that.birthDate);
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}
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@Override
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public int hashCode() {
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return Objects.hash(firstName, lastName);
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}
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}
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public static class PersonWithEqualsAndWrongComparable implements Comparable<PersonWithEqualsAndWrongComparable> {
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private String firstName;
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private String lastName;
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private LocalDate birthDate;
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public PersonWithEqualsAndWrongComparable(String firstName, String lastName) {
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if (firstName == null || lastName == null) {
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throw new NullPointerException("Names can't be null");
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}
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this.firstName = firstName;
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this.lastName = lastName;
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}
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public PersonWithEqualsAndWrongComparable(String firstName, String lastName, LocalDate birthDate) {
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this(firstName, lastName);
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this.birthDate = birthDate;
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}
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@Override
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public boolean equals(Object o) {
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if (this == o) return true;
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if (o == null || getClass() != o.getClass()) return false;
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PersonWithEqualsAndWrongComparable that = (PersonWithEqualsAndWrongComparable) o;
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return firstName.equals(that.firstName) &&
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lastName.equals(that.lastName) &&
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Objects.equals(birthDate, that.birthDate);
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}
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@Override
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public int hashCode() {
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return Objects.hash(firstName, lastName);
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}
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@Override
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public int compareTo(PersonWithEqualsAndWrongComparable o) {
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return this.lastName.compareTo(o.lastName);
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}
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}
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public static class PersonWithEqualsAndComparable implements Comparable<PersonWithEqualsAndComparable> {
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private String firstName;
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private String lastName;
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private LocalDate birthDate;
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public PersonWithEqualsAndComparable(String firstName, String lastName) {
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if (firstName == null || lastName == null) {
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throw new NullPointerException("Names can't be null");
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}
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this.firstName = firstName;
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this.lastName = lastName;
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}
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public PersonWithEqualsAndComparable(String firstName, String lastName, LocalDate birthDate) {
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this(firstName, lastName);
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this.birthDate = birthDate;
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}
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@Override
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public boolean equals(Object o) {
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if (this == o) return true;
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if (o == null || getClass() != o.getClass()) return false;
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PersonWithEqualsAndComparable that = (PersonWithEqualsAndComparable) o;
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return firstName.equals(that.firstName) &&
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lastName.equals(that.lastName) &&
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Objects.equals(birthDate, that.birthDate);
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}
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@Override
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public int hashCode() {
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return Objects.hash(firstName, lastName);
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}
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@Override
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public int compareTo(PersonWithEqualsAndComparable o) {
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int lastNamesComparison = this.lastName.compareTo(o.lastName);
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if (lastNamesComparison == 0) {
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int firstNamesComparison = this.firstName.compareTo(o.firstName);
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if (firstNamesComparison == 0) {
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if (this.birthDate != null && o.birthDate != null) {
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return this.birthDate.compareTo(o.birthDate);
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} else if (this.birthDate != null) {
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return 1;
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} else if (o.birthDate != null) {
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return -1;
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} else {
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return 0;
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}
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} else {
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return firstNamesComparison;
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}
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} else {
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return lastNamesComparison;
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}
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}
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}
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public static class PersonWithEqualsAndComparableUsingComparator implements Comparable<PersonWithEqualsAndComparableUsingComparator> {
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private String firstName;
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private String lastName;
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private LocalDate birthDate;
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public PersonWithEqualsAndComparableUsingComparator(String firstName, String lastName) {
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if (firstName == null || lastName == null) {
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throw new NullPointerException("Names can't be null");
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}
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this.firstName = firstName;
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this.lastName = lastName;
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}
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public PersonWithEqualsAndComparableUsingComparator(String firstName, String lastName, LocalDate birthDate) {
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this(firstName, lastName);
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this.birthDate = birthDate;
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}
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public String firstName() {
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return firstName;
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}
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public String lastName() {
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return lastName;
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}
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public LocalDate birthDate() {
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return birthDate;
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}
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@Override
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public boolean equals(Object o) {
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if (this == o) return true;
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if (o == null || getClass() != o.getClass()) return false;
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PersonWithEqualsAndComparableUsingComparator that = (PersonWithEqualsAndComparableUsingComparator) o;
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return firstName.equals(that.firstName) &&
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lastName.equals(that.lastName) &&
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Objects.equals(birthDate, that.birthDate);
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}
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@Override
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public int hashCode() {
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return Objects.hash(firstName, lastName);
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}
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@Override
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public int compareTo(PersonWithEqualsAndComparableUsingComparator o) {
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return Comparator.comparing(PersonWithEqualsAndComparableUsingComparator::lastName)
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.thenComparing(PersonWithEqualsAndComparableUsingComparator::firstName)
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.thenComparing(PersonWithEqualsAndComparableUsingComparator::birthDate, Comparator.nullsLast(Comparator.naturalOrder()))
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.compare(this, o);
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}
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}
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}

‎core-java-modules/core-java-lang-2/src/test/java/com/baeldung/comparing/ApacheCommonsObjectUtilsUnitTest.java‎

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package com.baeldung.comparing;
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import org.apache.commons.lang3.ObjectUtils;
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import org.junit.jupiter.api.Test;
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import static org.assertj.core.api.Assertions.assertThat;
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class ApacheCommonsObjectUtilsUnitTest {
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@Test
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void givenTwoStringsWithSameValues_whenApacheCommonsEqualityMethods_thenEqualsTrueNotEqualsFalse() {
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String a = new String("Hello!");
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String b = new String("Hello!");
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assertThat(ObjectUtils.equals(a, b)).isTrue();
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assertThat(ObjectUtils.notEqual(a, b)).isFalse();
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}
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@Test
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void givenTwoStringsWithDifferentValues_whenApacheCommonsEqualityMethods_thenEqualsFalseNotEqualsTrue() {
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String a = new String("Hello!");
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String b = new String("Hello World!");
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assertThat(ObjectUtils.equals(a, b)).isFalse();
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assertThat(ObjectUtils.notEqual(a, b)).isTrue();
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}
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@Test
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void givenTwoStringsWithConsecutiveValues_whenApacheCommonsCompare_thenNegative() {
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String first = new String("Hello!");
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String second = new String("How are you?");
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assertThat(ObjectUtils.compare(first, second)).isNegative();
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}
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@Test
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void givenTwoStringsWithSameValues_whenApacheCommonsEqualityMethods_thenEqualsFalseNotEqualsTrue() {
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String first = new String("Hello!");
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String second = new String("Hello!");
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assertThat(ObjectUtils.compare(first, second)).isZero();
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}
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@Test
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void givenTwoStringsWithConsecutiveValues_whenApacheCommonsCompareReversed_thenPositive() {
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String first = new String("Hello!");
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String second = new String("How are you?");
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assertThat(ObjectUtils.compare(second, first)).isPositive();
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}
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@Test
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void givenTwoStringsOneNull_whenApacheCommonsCompare_thenPositive() {
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String first = new String("Hello!");
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String second = null;
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assertThat(ObjectUtils.compare(first, second, false)).isPositive();
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}
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}

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