(#1566) Generify org.cactoos.list package

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

@@ -49,13 +49,13 @@ public final class Immutable<T> implements List<T> {
     /**
      * Encapsulated list.
      */
-    private final List<T> list;
+    private final List<? extends T> list;
 
     /**
      * Ctor.
      * @param src Source collection
      */
-    public Immutable(final List<T> src) {
+    public Immutable(final List<? extends T> src) {
         this.list = src;
     }
 

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

@@ -38,13 +38,13 @@ public final class ImmutableListIterator<T> implements ListIterator<T> {
     /**
      * Original list iterator.
      */
-    private final ListIterator<T> origin;
+    private final ListIterator<? extends T> origin;
 
     /**
      * Ctor.
      * @param iter Original list iterator.
      */
-    public ImmutableListIterator(final ListIterator<T> iter) {
+    public ImmutableListIterator(final ListIterator<? extends T> iter) {
         this.origin = iter;
     }
 

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

@@ -64,7 +64,7 @@ public Joined(final X item, final List<? extends X> items) {
      * Ctor.
      * @param src Source lists
      */
-    public Joined(final Iterable<List<? extends X>> src) {
+    public Joined(final Iterable<? extends List<? extends X>> src) {
         super(
             new ListOf<>(src).stream()
                 .flatMap(List::stream)

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

@@ -47,7 +47,7 @@ public final class JoinedListIterator<T> implements ListIterator<T> {
     /**
      * {@link List} of {@link ListIterator}.
      */
-    private final List<ListIterator<T>> listiters;
+    private final List<? extends ListIterator<? extends T>> listiters;
 
     /**
      * Cursor of the {@link List} of {@link ListIterator}.
@@ -64,7 +64,7 @@ public final class JoinedListIterator<T> implements ListIterator<T> {
      * @param items Items to concatenate
      */
     @SafeVarargs
-    public JoinedListIterator(final ListIterator<T>... items) {
+    public JoinedListIterator(final ListIterator<? extends T>... items) {
         this(new ListOf<>(items));
     }
 
@@ -74,7 +74,7 @@ public JoinedListIterator(final ListIterator<T>... items) {
      * @param items ListIterator
      */
     @SuppressWarnings("unchecked")
-    public JoinedListIterator(final T item, final ListIterator<T> items) {
+    public JoinedListIterator(final T item, final ListIterator<? extends T> items) {
         this(new ListOf<>(new ListOf<>(item).listIterator(), items));
     }
 
@@ -84,15 +84,15 @@ public JoinedListIterator(final T item, final ListIterator<T> items) {
      * @param item End item
      */
     @SuppressWarnings("unchecked")
-    public JoinedListIterator(final ListIterator<T> items, final T item) {
+    public JoinedListIterator(final ListIterator<? extends T> items, final T item) {
         this(new ListOf<>(items, new ListOf<>(item).listIterator()));
     }
 
     /**
      * Ctor.
      * @param items Items to concatenate
      */
-    public JoinedListIterator(final List<ListIterator<T>> items) {
+    public JoinedListIterator(final List<? extends ListIterator<? extends T>> items) {
         this.listiters = items;
         this.cursorlit = new AtomicInteger(-1);
         this.cursor = new AtomicInteger(-1);
@@ -183,8 +183,8 @@ private boolean listHasPreviousElt() {
      * Get current {@link ListIterator}.
      * @return Current element
      */
-    private ListIterator<T> currentListIterator() {
-        final ListIterator<T> current;
+    private ListIterator<? extends T> currentListIterator() {
+        final ListIterator<? extends T> current;
         if (this.cursorlit.get() == -1) {
             current = Collections.emptyListIterator();
         } else {

src/main/java/org/cactoos/list/package-info.java

@@ -26,8 +26,5 @@
  * Lists, tests.
  *
  * @since 0.14
- * @todo #1533:30min Exploit generic variance for package org.cactoos.list
- *  to ensure typing works as best as possible as it is explained in
- *  #1533 issue.
  */
 package org.cactoos.list;

src/test/java/org/cactoos/list/JoinedListIteratorTest.java

@@ -46,7 +46,7 @@ void joinsListIterators() {
         new Assertion<>(
             "Must concatenate iterable of listIterators together",
             new IterableOf<>(
-                new JoinedListIterator<>(
+                new JoinedListIterator<String>(
                     new ListOf<>("x").listIterator(),
                     new ListOf<>("y").listIterator()
                 )
@@ -60,7 +60,8 @@ void joinsListIterators() {
     void navigatesInNonEmptyIterator() {
         final ListIterator<Integer> joined = new JoinedListIterator<>(
             new ListOf<>(1).listIterator(),
-            new ListOf<>(2).listIterator()
+            new ListOf<>(2).listIterator(),
+            new ListOf<>(3).listIterator()
         );
         new Assertion<>(
             "Must call next method directly on non-empty listIterator for the first time",