Merge pull request #9852 from alimate/BAEL-4536

BAEL-4536: Improvement - compareTo Implementations

core-java-modules/core-java-collections-2/src/test/java/com/baeldung/collections/sorting/JavaSortingUnitTest.java

@@ -5,7 +5,16 @@ import org.apache.commons.lang3.ArrayUtils;
 import org.junit.Before;
 import org.junit.Test;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
 import java.util.Map.Entry;
 
 import static org.junit.Assert.assertTrue;
@@ -138,7 +147,7 @@ public class JavaSortingUnitTest {
         HashSet<Integer> descSortedIntegersSet = new LinkedHashSet<>(Arrays.asList(255, 200, 123, 89, 88, 66, 7, 5, 1));
 
         ArrayList<Integer> list = new ArrayList<>(integersSet);
-        list.sort((i1, i2) -> i2 - i1);
+        list.sort(Comparator.reverseOrder());
         integersSet = new LinkedHashSet<>(list);
 
         assertTrue(Arrays.equals(integersSet.toArray(), descSortedIntegersSet.toArray()));

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/java8/entity/Human.java

@@ -37,7 +37,7 @@ public class Human {
 
     public static int compareByNameThenAge(final Human lhs, final Human rhs) {
         if (lhs.name.equals(rhs.name)) {
-            return lhs.age - rhs.age;
+            return Integer.compare(lhs.age, rhs.age);
         } else {
             return lhs.name.compareTo(rhs.name);
         }

core-java-modules/core-java-lambdas/src/test/java/com/baeldung/java8/Java8SortUnitTest.java

@@ -54,7 +54,7 @@ public class Java8SortUnitTest {
         final List<Human> humans = Lists.newArrayList(new Human("Sarah", 12), new Human("Sarah", 10), new Human("Zack", 12));
         humans.sort((lhs, rhs) -> {
             if (lhs.getName().equals(rhs.getName())) {
-                return lhs.getAge() - rhs.getAge();
+                return Integer.compare(lhs.getAge(), rhs.getAge());
             } else {
                 return lhs.getName().compareTo(rhs.getName());
             }

core-java-modules/core-java-lang/src/main/java/com/baeldung/comparable/Player.java

@@ -45,7 +45,7 @@ public class Player implements Comparable<Player> {
 
     @Override
     public int compareTo(Player otherPlayer) {
-        return (this.getRanking() - otherPlayer.getRanking());
+        return Integer.compare(getRanking(), otherPlayer.getRanking());
     }
 
 }

core-java-modules/core-java-lang/src/main/java/com/baeldung/comparator/PlayerAgeComparator.java

@@ -6,7 +6,7 @@ public class PlayerAgeComparator implements Comparator<Player> {
 
     @Override
     public int compare(Player firstPlayer, Player secondPlayer) {
-       return (firstPlayer.getAge() - secondPlayer.getAge());
+       return Integer.compare(firstPlayer.getAge(), secondPlayer.getAge());
     }
 
 }

core-java-modules/core-java-lang/src/main/java/com/baeldung/comparator/PlayerRankingComparator.java

@@ -6,7 +6,7 @@ public class PlayerRankingComparator implements Comparator<Player> {
 
     @Override
     public int compare(Player firstPlayer, Player secondPlayer) {
-       return (firstPlayer.getRanking() - secondPlayer.getRanking());
+       return Integer.compare(firstPlayer.getRanking(), secondPlayer.getRanking());
     }
 
 }

core-java-modules/core-java-lang/src/test/java/com/baeldung/comparator/AvoidingSubtractionUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.comparator;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class AvoidingSubtractionUnitTest {
+
+    @Test
+    public void givenTwoPlayers_whenUsingSubtraction_thenOverflow() {
+        Comparator<Player> comparator = (p1, p2) -> p1.getRanking() - p2.getRanking();
+        Player player1 = new Player(59, "John", Integer.MAX_VALUE);
+        Player player2 = new Player(67, "Roger", -1);
+
+        List<Player> players = Arrays.asList(player1, player2);
+        players.sort(comparator);
+        System.out.println(players);
+
+        assertEquals("John", players.get(0).getName());
+        assertEquals("Roger", players.get(1).getName());
+    }
+}

core-java-modules/core-java-lang/src/test/java/com/baeldung/comparator/Java8ComparatorUnitTest.java

@@ -1,14 +1,14 @@
 package com.baeldung.comparator;
 
-import static org.junit.Assert.assertEquals;
+import org.junit.Before;
+import org.junit.Test;
 
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
-import org.junit.Before;
-import org.junit.Test;
+import static org.junit.Assert.assertEquals;
 
 public class Java8ComparatorUnitTest {
 
@@ -28,7 +28,7 @@ public class Java8ComparatorUnitTest {
     @Test
     public void whenComparing_UsingLambda_thenSorted() {
         System.out.println("************** Java 8 Comaparator **************");
-        Comparator<Player> byRanking = (Player player1, Player player2) -> player1.getRanking() - player2.getRanking();
+        Comparator<Player> byRanking = (Player player1, Player player2) -> Integer.compare(player1.getRanking(), player2.getRanking());
 
         System.out.println("Before Sorting : " + footballTeam);
         Collections.sort(footballTeam, byRanking);