yegor256#881 equals and hashCode for CollectionEnvelope

src/main/java/org/cactoos/collection/CollectionEnvelope.java

@@ -27,19 +27,23 @@
 import java.util.Iterator;
 import org.cactoos.Scalar;
 import org.cactoos.iterator.Immutable;
+import org.cactoos.scalar.And;
+import org.cactoos.scalar.Folded;
+import org.cactoos.scalar.InheritanceLevel;
+import org.cactoos.scalar.Or;
+import org.cactoos.scalar.SumOfIntScalar;
 import org.cactoos.scalar.UncheckedScalar;
 
 /**
  * Base collection.
  *
  * <p>There is no thread-safety guarantee.</p>
- *
  * @param <X> Element type
- * @since 0.23
  * @todo #844:30min Implement methods equals and hashCode for this class.
- *  Implementation should rely on the items of the nested collection, but not
- *  on default JVM impl. Class {@link org.cactoos.map.MapEnvelope} can be used
- *  as an example.
+ * Implementation should rely on the items of the nested collection, but not
+ * on default JVM impl. Class {@link org.cactoos.map.MapEnvelope} can be used
+ * as an example.
+ * @since 0.23
  * @checkstyle AbstractClassNameCheck (500 lines)
  */
 @SuppressWarnings(
@@ -147,4 +151,48 @@ public String toString() {
         return this.col.value().toString();
     }
 
+    @Override
+    public final boolean equals(final Object other) {
+        return new UncheckedScalar<>(
+            new And(
+                new Or(
+                    () -> new InheritanceLevel(
+                        other.getClass(), Collection.class
+                    ).value() > -1,
+                    () -> new InheritanceLevel(
+                        other.getClass(), CollectionEnvelope.class
+                    ).value() > -1
+                ),
+                () -> {
+                    final Collection<?> compared = (Collection<?>) other;
+                    return this.size() == compared.size();
+                },
+                () -> {
+                    final Iterable<?> compared = (Iterable<?>) other;
+                    final Iterator<?> iterator = compared.iterator();
+                    return new UncheckedScalar<>(
+                        new And(
+                            (X input) -> input.equals(iterator.next()),
+                            this
+                        )
+                    ).value();
+                }
+            )
+        ).value();
+    }
+
+    // @checkstyle MagicNumberCheck (30 lines)
+    @Override
+    public final int hashCode() {
+        return new UncheckedScalar<>(
+            new Folded<>(
+                42,
+                (hash, entry) -> new SumOfIntScalar(
+                    () -> 37 * hash,
+                    entry::hashCode
+                ).value(),
+                this
+            )
+        ).value();
+    }
 }

src/main/java/org/cactoos/list/ListEnvelope.java

@@ -113,16 +113,6 @@ public final List<T> subList(final int start, final int end) {
         return this.list.value().subList(start, end);
     }
 
-    @Override
-    public boolean equals(final Object obj) {
-        return this.list.value().equals(obj);
-    }
-
-    @Override
-    public int hashCode() {
-        return this.list.value().hashCode();
-    }
-
     @Override
     public String toString() {
         return this.list.value().toString();

src/test/java/org/cactoos/collection/CollectionEnvelopeTest.java

@@ -26,6 +26,10 @@
 import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
+import org.cactoos.list.ListOf;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.core.IsEqual;
+import org.hamcrest.core.IsNot;
 import org.junit.Test;
 
 /**
@@ -37,6 +41,7 @@
  *  Iterator for IterableEnvelope `iterator()` method.
  * @checkstyle JavadocMethodCheck (500 lines)
  */
+@SuppressWarnings("PMD.AvoidDuplicateLiterals")
 public final class CollectionEnvelopeTest {
     @Test(expected = UnsupportedOperationException.class)
     public void returnsIteratorWithUnsupportedRemove() {
@@ -51,4 +56,99 @@ public void returnsIteratorWithUnsupportedRemove() {
         iterator.next();
         iterator.remove();
     }
+
+    @Test
+    public void notEqualToObjectOfAnotherType() {
+        MatcherAssert.assertThat(
+            "Collection is equal to object of different type",
+            new CollectionOf<>(),
+            new IsNot<>(new IsEqual<>("a"))
+        );
+    }
+
+    @Test
+    public void notEqualToCollectionOfDifferentSize() {
+        MatcherAssert.assertThat(
+            "Collection is equal to a collection of different size",
+            new CollectionOf<>(),
+            new IsNot<>(new IsEqual<>(new CollectionOf<>("b")))
+        );
+    }
+
+    @Test
+    public void notEqualToCollectionOfDifferentElements() {
+        MatcherAssert.assertThat(
+            "Collection is equal to a collection with different content",
+            new CollectionOf<>("a", "b"),
+            new IsNot<>(new IsEqual<>(new CollectionOf<>("a", "c")))
+        );
+    }
+
+    @Test
+    public void equalToCollectionWithIdenticalContent() {
+        MatcherAssert.assertThat(
+            "Collection is not equal to a collection with identical content",
+            new CollectionOf<>("val1", "val2"),
+            new IsEqual<>(new CollectionOf<>("val1", "val2"))
+        );
+    }
+
+    @Test
+    public void equalToListWithIdenticalContent() {
+        MatcherAssert.assertThat(
+            "Collection not equal to a list with identical content",
+            new CollectionOf<>("a"),
+            new IsEqual<>(new ListOf<>("a"))
+        );
+    }
+
+    @Test
+    public void equalToDerivedCollection() {
+        MatcherAssert.assertThat(
+            "Collection not equal to derived collection with identical content",
+            new CollectionOf<>("a"),
+            new IsEqual<>(new CollectionEnvelopeTest.CustomCollection("a"))
+        );
+    }
+
+    @Test
+    public void equalToEmptyCollection() {
+        MatcherAssert.assertThat(
+            "Empty collection not equal with empty collection",
+            new CollectionOf<>(),
+            new IsEqual<>(new CollectionOf<>())
+        );
+    }
+
+    @Test
+    public void hashCodeEqual() {
+        MatcherAssert.assertThat(
+            "HashCode returns different results for same entries",
+            new CollectionOf<>("a", "b").hashCode(),
+            new IsEqual<>(new CollectionOf<>("a", "b").hashCode())
+        );
+    }
+
+    @Test
+    public void differentHashCode() {
+        MatcherAssert.assertThat(
+            "HashCode returns identical results for different entries",
+            new CollectionOf<>("a", "b").hashCode(),
+            new IsNot<>(new IsEqual<>(new CollectionOf<>("b", "a").hashCode()))
+        );
+    }
+
+    /**
+     * Custom collection.
+     */
+    private static class CustomCollection extends CollectionEnvelope<String> {
+
+        /**
+         * Ctor.
+         * @param elements String elements
+         */
+        CustomCollection(final String... elements) {
+            super(() -> new CollectionOf<>(elements));
+        }
+    }
 }