listOfLists article (#12078)

core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/list/listoflists/ListOfListsUnitTest.java

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+package com.baeldung.list.listoflists;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Test;
+
+public class ListOfListsUnitTest {
+
+    private List<List<String>> getListOfListsFromCsv() throws URISyntaxException, IOException {
+
+        List<String> lines = Files.readAllLines(Paths.get(getClass().getResource("/listoflists/example.csv")
+            .toURI()));
+        List<List<String>> listOfLists = new ArrayList<>();
+
+        lines.forEach(line -> {
+            List<String> innerList = new ArrayList<>(Arrays.asList(line.split(", ")));
+            listOfLists.add(innerList);
+        });
+        return listOfLists;
+    }
+
+    private void printListOfLists(List<List<String>> listOfLists) {
+        System.out.println("\n           List of Lists           ");
+        System.out.println("-------------------------------------");
+        listOfLists.forEach(innerList -> {
+            String line = String.join(", ", innerList);
+            System.out.println(line);
+        });
+    }
+
+    @Test
+    void givenCsv_whenInitListOfLists_thenGetExpectedResults() throws URISyntaxException, IOException {
+        List<List<String>> listOfLists = getListOfListsFromCsv();
+        assertThat(listOfLists).hasSize(3);
+        assertThat(listOfLists.stream()
+            .map(List::size)
+            .collect(Collectors.toSet())).hasSize(1)
+            .containsExactly(4);
+        printListOfLists(listOfLists);
+    }
+
+    @Test
+    void givenListOfLists_whenRemoveElementFromInnerLists_thenGetExpectedResults() throws URISyntaxException, IOException {
+        List<List<String>> listOfLists = getListOfListsFromCsv();
+
+        listOfLists.forEach(innerList -> innerList.remove("Delete Me"));
+        assertThat(listOfLists.stream()
+            .map(List::size)
+            .collect(Collectors.toSet())).hasSize(1)
+            .containsExactly(3);
+
+        printListOfLists(listOfLists);
+    }
+
+    @Test
+    void givenListOfLists_whenAddNewInnerList_thenGetExpectedResults() throws URISyntaxException, IOException {
+        List<List<String>> listOfLists = getListOfListsFromCsv();
+        List<String> newList = new ArrayList<>(Arrays.asList("Slack", "Zoom", "Microsoft Teams", "Telegram"));
+        listOfLists.add(2, newList);
+
+        assertThat(listOfLists).hasSize(4);
+        assertThat(listOfLists.get(2)).containsExactly("Slack", "Zoom", "Microsoft Teams", "Telegram");
+        printListOfLists(listOfLists);
+    }
+}

core-java-modules/core-java-collections-list-3/src/test/resources/listoflists/example.csv

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+Linux, Microsoft Windows, Mac OS, Delete Me
+Kotlin, Delete Me, Java, Python
+Delete Me, Mercurial, Git, Subversion