CustomLinkedList implements Collection instead of Iterable

Author: andrei-punko

src/main/java/by/andd3dfx/collections/custom/CustomLinkedList.java

@@ -1,13 +1,15 @@
 package by.andd3dfx.collections.custom;
 
 import lombok.AllArgsConstructor;
+import org.apache.commons.lang3.NotImplementedException;
 
+import java.util.Collection;
 import java.util.Iterator;
 
 /**
  * @see <a href="https://youtu.be/vHjvNHBQP3o">Video solution</a>
  */
-public class CustomLinkedList<T> implements Iterable<T> {
+public class CustomLinkedList<T> implements Collection<T> {
 
     @AllArgsConstructor
     public static class Node<M> {
@@ -26,8 +28,10 @@ public String toString() {
     private Node<T> head;
     private int size = 0;
 
-    public void add(T value) {
+    @Override
+    public boolean add(T value) {
         add(size, value);
+        return true;
     }
 
     public void add(int index, T value) {
@@ -53,14 +57,37 @@ public void add(int index, T value) {
         size++;
     }
 
+    @Override
     public int size() {
         return size;
     }
 
+    @Override
     public boolean isEmpty() {
         return size == 0;
     }
 
+    @Override
+    public boolean contains(Object o) {
+        var curr = head;
+        if (o == null) {
+            while (curr != null) {
+                if (curr.value == null) {
+                    return true;
+                }
+                curr = curr.next;
+            }
+        } else {
+            while (curr != null) {
+                if (o.equals(curr.value)) {
+                    return true;
+                }
+                curr = curr.next;
+            }
+        }
+        return false;
+    }
+
     public T get(int index) {
         if (index < 0 || index >= size) {
             throw new IndexOutOfBoundsException(String.format("Wrong index: %d", index));
@@ -120,7 +147,8 @@ public T remove(int index) {
         return curr.value;
     }
 
-    public boolean remove(T value) {
+    @Override
+    public boolean remove(Object value) {
         var i = 0;
         var curr = head;
         while (curr != null) {
@@ -134,7 +162,35 @@ public boolean remove(T value) {
         return false;
     }
 
-    private boolean checkEquality(T value1, T value2) {
+    @Override
+    public boolean containsAll(Collection<?> c) {
+        for (var element : c) {
+            if (!contains(element)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    @Override
+    public boolean addAll(Collection<? extends T> c) {
+        // TODO add implementation
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public boolean removeAll(Collection<?> c) {
+        // TODO add implementation
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public boolean retainAll(Collection<?> c) {
+        // TODO add implementation
+        throw new UnsupportedOperationException();
+    }
+
+    private boolean checkEquality(Object value1, Object value2) {
         if (value1 == null) {
             return value2 == null;
         }
@@ -162,6 +218,7 @@ public void reverse() {
         head = prev;
     }
 
+    @Override
     public void clear() {
         head = null;
         size = 0;
@@ -172,6 +229,18 @@ public Iterator<T> iterator() {
         return new CustomIterator<>(head);
     }
 
+    @Override
+    public Object[] toArray() {
+        // TODO add implementation
+        throw new NotImplementedException();
+    }
+
+    @Override
+    public <T1> T1[] toArray(T1[] a) {
+        // TODO add implementation
+        throw new NotImplementedException();
+    }
+
     @AllArgsConstructor
     public static class CustomIterator<E> implements Iterator<E> {
         private Node<E> curr;

src/test/java/by/andd3dfx/collections/custom/CustomLinkedListTest.java

@@ -3,6 +3,7 @@
 import org.junit.Test;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -18,8 +19,8 @@ public void addNGet() {
         assertThat(linkedList.size()).isEqualTo(0);
         assertTrue(linkedList.isEmpty());
 
-        linkedList.add(3);
-        linkedList.add(7);
+        assertTrue(linkedList.add(3));
+        assertTrue(linkedList.add(7));
 
         assertThat(linkedList.size()).isEqualTo(2);
         assertFalse(linkedList.isEmpty());
@@ -340,4 +341,32 @@ public void testToString() {
 
         assertThat(result).isEqualTo("CustomLinkedList{head={3, next={7, next={12, next={34}}}}}");
     }
+
+    @Test
+    public void contains() {
+        var linkedList = new CustomLinkedList<>();
+        linkedList.add(3);
+        linkedList.add(7);
+        assertThat(linkedList.contains(null)).isFalse();
+
+        linkedList.add(null);
+        linkedList.add(12);
+        assertThat(linkedList.contains(3)).isTrue();
+        assertThat(linkedList.contains(99)).isFalse();
+        assertThat(linkedList.contains(12)).isTrue();
+        assertThat(linkedList.contains(null)).isTrue();
+    }
+
+    @Test
+    public void containsAll() {
+        var linkedList = new CustomLinkedList<>();
+        linkedList.add(3);
+        linkedList.add(7);
+        linkedList.add(null);
+        linkedList.add(99);
+
+        assertThat(linkedList.containsAll(List.of(3, 99))).isTrue();
+        assertThat(linkedList.containsAll(Arrays.asList(7, null, 99))).isTrue();
+        assertThat(linkedList.containsAll(List.of(7, 12))).isFalse();
+    }
 }