BAEL-7910: Avoid Inserting Duplicate in ArrayList in Java (#16730)

Author: azhwani

core-java-modules/core-java-collections-array-list-2/src/test/java/com/baeldung/avoidduplicatearraylist/AvoidDuplicateInArrayListUnitTest.java

@@ -0,0 +1,102 @@
+package com.baeldung.avoidduplicatearraylist;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+
+import org.apache.commons.collections4.CollectionUtils;
+import org.junit.jupiter.api.Test;
+
+import com.google.common.collect.Iterables;
+
+class AvoidDuplicateInArrayListUnitTest {
+
+    @Test
+    void givenArrayList_whenUsingSet_thenAvoidDuplicates() {
+        Set<String> distinctCities = new HashSet<>(Arrays.asList("Tamassint", "Madrid", "Paris", "Tokyo"));
+
+        String newCity = "Paris";
+        distinctCities.add(newCity);
+        ArrayList<String> arrayListCities = new ArrayList<>(distinctCities);
+
+        assertThat(arrayListCities).hasSameSizeAs(distinctCities);
+    }
+
+    @Test
+    void givenArrayList_whenUsingContains_thenAvoidDuplicates() {
+        List<String> distinctCities = Arrays.asList("Tamassint", "Madrid", "Paris", "Tokyo");
+        ArrayList<String> arrayListCities = new ArrayList<>(distinctCities);
+
+        String newCity = "Madrid";
+        if (!arrayListCities.contains(newCity)) {
+            arrayListCities.add(newCity);
+        }
+
+        assertThat(arrayListCities).hasSameSizeAs(distinctCities);
+    }
+
+    @Test
+    void givenArrayList_whenUsingAnyMatch_thenAvoidDuplicates() {
+        List<String> distinctCities = Arrays.asList("Tamassint", "Madrid", "Paris", "Tokyo");
+        ArrayList<String> arrayListCities = new ArrayList<>(distinctCities);
+
+        String newCity = "Tamassint";
+        boolean isCityPresent = arrayListCities.stream()
+            .anyMatch(city -> city.equals(newCity));
+        if (!isCityPresent) {
+            arrayListCities.add(newCity);
+        }
+
+        assertThat(arrayListCities).hasSameSizeAs(distinctCities);
+    }
+
+    @Test
+    void givenArrayList_whenUsingFilterAndFindFirst_thenAvoidDuplicates() {
+        List<String> distinctCities = Arrays.asList("Tamassint", "Madrid", "Paris", "Tokyo");
+        ArrayList<String> arrayListCities = new ArrayList<>(distinctCities);
+
+        String newCity = "Tamassint";
+        Optional<String> optionalCity = arrayListCities.stream()
+            .filter(city -> city.equals(newCity))
+            .findFirst();
+        if (optionalCity.isEmpty()) {
+            arrayListCities.add(newCity);
+        }
+
+        assertThat(arrayListCities).hasSameSizeAs(distinctCities);
+    }
+
+    @Test
+    void givenArrayList_whenUsingCollectionUtilsContainsAny_thenAvoidDuplicates() {
+        List<String> distinctCities = Arrays.asList("Tamassint", "Madrid", "Paris", "Tokyo");
+        ArrayList<String> arrayListCities = new ArrayList<>(distinctCities);
+
+        String newCity = "Tokyo";
+        boolean isCityPresent = CollectionUtils.containsAny(arrayListCities, newCity);
+        if (!isCityPresent) {
+            arrayListCities.add(newCity);
+        }
+
+        assertThat(arrayListCities).hasSameSizeAs(distinctCities);
+    }
+
+    @Test
+    void givenArrayList_whenUsingIterablesContains_thenAvoidDuplicates() {
+        List<String> distinctCities = Arrays.asList("Tamassint", "Madrid", "Paris", "Tokyo");
+        ArrayList<String> arrayListCities = new ArrayList<>(distinctCities);
+
+        String newCity = "Paris";
+        boolean isCityPresent = Iterables.contains(arrayListCities, newCity);
+        if (!isCityPresent) {
+            arrayListCities.add(newCity);
+        }
+
+        assertThat(arrayListCities).hasSameSizeAs(distinctCities);
+    }
+
+}