Create ArrayList demo (#643)

core-java/src/test/java/org/baeldung/java/collections/ArrayListTest.java

@@ -0,0 +1,148 @@
+package org.baeldung.java.collections;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.*;
+import java.util.stream.*;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.core.IsNot.not;
+import static org.junit.Assert.*;
+
+public class ArrayListTest {
+
+    List<String> stringsToSearch;
+
+    @Before
+    public void setUp() {
+        List<String> xs = LongStream.range(0, 16)
+            .boxed()
+            .map(Long::toHexString)
+            .collect(Collectors.toList());
+        stringsToSearch = new ArrayList<>(xs);
+        stringsToSearch.addAll(xs);
+    }
+
+    @Test
+    public void givenNewArrayList_whenCheckCapacity_thenDefaultValue() {
+        List<String> xs = new ArrayList<>();
+        assertTrue(xs.isEmpty());
+    }
+
+    @Test
+    public void givenCollection_whenProvideItToArrayListCtor_thenArrayListIsPopulatedWithItsElements() {
+        Collection<Integer> numbers =
+            IntStream.range(0, 10).boxed().collect(Collectors.toSet());
+
+        List<Integer> xs = new ArrayList<>(numbers);
+        assertEquals(10, xs.size());
+        assertTrue(numbers.containsAll(xs));
+    }
+
+    @Test
+    public void givenElement_whenAddToArrayList_thenIsAdded() {
+        List<Long> xs = new ArrayList<>();
+
+        xs.add(1L);
+        xs.add(2L);
+        xs.add(1, 3L);
+
+        assertThat(Arrays.asList(1L, 3L, 2L), equalTo(xs));
+    }
+
+    @Test
+    public void givenCollection_whenAddToArrayList_thenIsAdded() {
+        List<Long> xs = new ArrayList<>(Arrays.asList(1L, 2L, 3L));
+        Collection<Long> ys = LongStream.range(4, 10).boxed().collect(Collectors.toList());
+        xs.addAll(0, ys);
+
+        assertThat(Arrays.asList(4L, 5L, 6L, 7L, 8L, 9L, 1L, 2L, 3L), equalTo(xs));
+    }
+
+    @Test
+    public void givenExistingElement_whenCallIndexOf_thenReturnCorrectIndex() {
+        assertEquals(10, stringsToSearch.indexOf("a"));
+        assertEquals(26, stringsToSearch.lastIndexOf("a"));
+    }
+
+    @Test
+    public void givenCondition_whenIterateArrayList_thenFindAllElementsSatisfyingCondition() {
+        Iterator<String> it = stringsToSearch.iterator();
+        Set<String> matchingStrings = new HashSet<>(Arrays.asList("a", "c", "9"));
+
+        List<String> result = new ArrayList<>();
+        while (it.hasNext()) {
+            String s = it.next();
+            if (matchingStrings.contains(s)) {
+                result.add(s);
+            }
+        }
+
+        assertEquals(6, result.size());
+    }
+
+    @Test
+    public void givenPredicate_whenIterateArrayList_thenFindAllElementsSatisfyingPredicate() {
+        Set<String> matchingStrings = new HashSet<>(Arrays.asList("a", "c", "9"));
+
+        List<String> result = stringsToSearch
+            .stream()
+            .filter(matchingStrings::contains)
+            .collect(Collectors.toList());
+
+        assertEquals(6, result.size());
+    }
+
+    @Test
+    public void givenSortedArray_whenUseBinarySearch_thenFindElement() {
+        List<String> copy = new ArrayList<>(stringsToSearch);
+        Collections.sort(copy);
+        int index = Collections.binarySearch(copy, "f");
+        assertThat(index, not(equalTo(-1)));
+    }
+
+    @Test
+    public void givenIndex_whenRemove_thenCorrectElementRemoved() {
+        List<Integer> xs = new ArrayList<>(
+            IntStream.range(0, 10).boxed().collect(Collectors.toList())
+        );
+        Collections.reverse(xs);
+
+        xs.remove(0);
+        assertThat(xs.get(0), equalTo(8));
+
+        xs.remove(Integer.valueOf(0));
+        assertFalse(xs.contains(0));
+    }
+
+    @Test
+    public void givenListIterator_whenReverseTraversal_thenRetrieveElementsInOppositeOrder() {
+        List<Integer> xs = new ArrayList<>(
+            IntStream.range(0, 10).boxed().collect(Collectors.toList())
+        );
+        ListIterator<Integer> it = xs.listIterator(xs.size());
+        List<Integer> result = new ArrayList<>(xs.size());
+        while (it.hasPrevious()) {
+            result.add(it.previous());
+        }
+
+        Collections.reverse(xs);
+        assertThat(result, equalTo(xs));
+    }
+
+    @Test
+    public void givenCondition_whenIterateArrayList_thenRemoveAllElementsSatisfyingCondition() {
+        Set<String> matchingStrings
+            = new HashSet<>(Arrays.asList("a", "b", "c", "d", "e", "f"));
+
+        Iterator<String> it = stringsToSearch.iterator();
+        while (it.hasNext()) {
+            if (matchingStrings.contains(it.next())) {
+                it.remove();
+            }
+        }
+
+        assertEquals(20, stringsToSearch.size());
+    }
+}