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JonCookJonCook
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Merge pull request eugenp#10443 from dstr89/feature/BAEL-4535-overriding-compareTo
Feature/bael 4535 overriding compare to
2 parents 79420a9 + cba9eed commit 51b6942

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‎core-java-modules/core-java-lang-3/src/main/java/com/baeldung/compareto/BankAccount.java‎

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package com.baeldung.compareto;
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public class BankAccount implements Comparable<BankAccount> {
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private final int balance;
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public BankAccount(int balance) {
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this.balance = balance;
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}
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@Override
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public int compareTo(BankAccount anotherAccount) {
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return this.balance - anotherAccount.balance;
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}
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}

‎core-java-modules/core-java-lang-3/src/main/java/com/baeldung/compareto/BankAccountFix.java‎

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package com.baeldung.compareto;
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public class BankAccountFix implements Comparable<BankAccountFix> {
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private final int balance;
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public BankAccountFix(int balance) {
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this.balance = balance;
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}
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@Override
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public int compareTo(BankAccountFix anotherAccount) {
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return Integer.compare(this.balance, anotherAccount.balance);
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}
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}

‎core-java-modules/core-java-lang-3/src/main/java/com/baeldung/compareto/FootballPlayer.java‎

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package com.baeldung.compareto;
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public class FootballPlayer implements Comparable<FootballPlayer> {
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private final String name;
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private final int goalsScored;
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public FootballPlayer(String name, int goalsScored) {
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this.name = name;
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this.goalsScored = goalsScored;
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}
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public String getName() {
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return name;
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}
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@Override
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public int compareTo(FootballPlayer anotherPlayer) {
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return Integer.compare(this.goalsScored, anotherPlayer.goalsScored);
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}
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@Override
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public boolean equals(Object object) {
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if (this == object)
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return true;
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if (object == null || getClass() != object.getClass())
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return false;
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FootballPlayer player = (FootballPlayer) object;
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return name.equals(player.name);
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}
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}

‎core-java-modules/core-java-lang-3/src/main/java/com/baeldung/compareto/HandballPlayer.java‎

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package com.baeldung.compareto;
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public class HandballPlayer {
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private final String name;
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private final int height;
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public HandballPlayer(String name, int height) {
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this.name = name;
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this.height = height;
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}
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}

‎core-java-modules/core-java-lang-3/src/test/java/com/baeldung/compareto/ArraysSortingUnitTest.java‎

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package com.baeldung.compareto;
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import org.junit.jupiter.api.Test;
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import java.util.Arrays;
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import static org.assertj.core.api.Assertions.assertThat;
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public class ArraysSortingUnitTest {
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@Test
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public void givenArrayOfNumbers_whenSortingArray_thenNumbersAreSortedAscending() {
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int[] numbers = new int[] {5, 3, 9, 11, 1, 7};
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Arrays.sort(numbers);
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assertThat(numbers).containsExactly(1, 3, 5, 7, 9, 11);
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}
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@Test
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public void givenArrayOfStrings_whenSortingArray_thenStringsAreSortedAlphabetically() {
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String[] players = new String[] {"ronaldo", "modric", "ramos", "messi"};
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Arrays.sort(players);
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assertThat(players).containsExactly("messi", "modric", "ramos", "ronaldo");
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}
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}

‎core-java-modules/core-java-lang-3/src/test/java/com/baeldung/compareto/BankAccountFixUnitTest.java‎

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package com.baeldung.compareto;
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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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public class BankAccountFixUnitTest {
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@Test
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public void givenComparisonBasedImpl_whenUsingSmallIntegers_thenComparisonWorks() {
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BankAccountFix accountOne = new BankAccountFix(5000);
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BankAccountFix accountTwo = new BankAccountFix(1000);
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int comparison = accountOne.compareTo(accountTwo);
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assertThat(comparison).isPositive();
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}
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@Test
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public void givenComparisonBasedImpl_whenUsingLargeIntegers_thenComparisonWorks() {
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BankAccountFix accountOne = new BankAccountFix(1900000000);
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BankAccountFix accountTwo = new BankAccountFix(-2000000000);
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int comparison = accountOne.compareTo(accountTwo);
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assertThat(comparison).isPositive();
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}
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}

‎core-java-modules/core-java-lang-3/src/test/java/com/baeldung/compareto/BankAccountUnitTest.java‎

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package com.baeldung.compareto;
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import org.junit.jupiter.api.Test;
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import static org.assertj.core.api.Assertions.*;
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public class BankAccountUnitTest {
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@Test
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public void givenSubtractionBasedImpl_whenUsingSmallIntegers_thenComparisonWorks() {
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BankAccount accountOne = new BankAccount(5000);
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BankAccount accountTwo = new BankAccount(1000);
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int comparison = accountOne.compareTo(accountTwo);
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assertThat(comparison).isPositive();
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}
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@Test
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public void givenSubtractionBasedImpl_whenUsingLargeIntegers_thenComparisonBreaks() {
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BankAccount accountOne = new BankAccount(1900000000);
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BankAccount accountTwo = new BankAccount(-2000000000);
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int comparison = accountOne.compareTo(accountTwo);
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assertThat(comparison).isNegative();
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}
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}

‎core-java-modules/core-java-lang-3/src/test/java/com/baeldung/compareto/FootballPlayerUnitTest.java‎

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package com.baeldung.compareto;
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import org.junit.jupiter.api.Test;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.Comparator;
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import java.util.List;
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import java.util.Map;
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import java.util.TreeMap;
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import java.util.TreeSet;
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import static org.assertj.core.api.Assertions.assertThat;
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public class FootballPlayerUnitTest {
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@Test
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public void givenInconsistentCompareToAndEqualsImpl_whenUsingSortedSet_thenSomeElementsAreNotAdded() {
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FootballPlayer messi = new FootballPlayer("Messi", 800);
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FootballPlayer ronaldo = new FootballPlayer("Ronaldo", 800);
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TreeSet<FootballPlayer> set = new TreeSet<>();
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set.add(messi);
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set.add(ronaldo);
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assertThat(set).hasSize(1);
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assertThat(set).doesNotContain(ronaldo);
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}
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@Test
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public void givenCompareToImpl_whenUsingCustomComparator_thenComparatorLogicIsApplied() {
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FootballPlayer ronaldo = new FootballPlayer("Ronaldo", 900);
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FootballPlayer messi = new FootballPlayer("Messi", 800);
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FootballPlayer modric = new FootballPlayer("Modric", 100);
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List<FootballPlayer> players = Arrays.asList(ronaldo, messi, modric);
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Comparator<FootballPlayer> nameComparator = Comparator.comparing(FootballPlayer::getName);
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Collections.sort(players, nameComparator);
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assertThat(players).containsExactly(messi, modric, ronaldo);
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}
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@Test
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public void givenCompareToImpl_whenSavingElementsInTreeMap_thenKeysAreSortedUsingCompareTo() {
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FootballPlayer ronaldo = new FootballPlayer("Ronaldo", 900);
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FootballPlayer messi = new FootballPlayer("Messi", 800);
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FootballPlayer modric = new FootballPlayer("Modric", 100);
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Map<FootballPlayer, String> players = new TreeMap<>();
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players.put(ronaldo, "forward");
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players.put(messi, "forward");
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players.put(modric, "midfielder");
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assertThat(players.keySet()).containsExactly(modric, messi, ronaldo);
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}
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}

‎core-java-modules/core-java-lang-3/src/test/java/com/baeldung/compareto/HandballPlayerUnitTest.java‎

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package com.baeldung.compareto;
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import org.junit.jupiter.api.Test;
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import java.util.Arrays;
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import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
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public class HandballPlayerUnitTest {
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@Test
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public void givenComparableIsNotImplemented_whenSortingArray_thenExceptionIsThrown() {
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HandballPlayer duvnjak = new HandballPlayer("Duvnjak", 197);
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HandballPlayer hansen = new HandballPlayer("Hansen", 196);
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HandballPlayer[] players = new HandballPlayer[] {duvnjak, hansen};
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assertThatExceptionOfType(ClassCastException.class).isThrownBy(() -> Arrays.sort(players));
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}
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}

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