src/java.base/share/classes/java/util/List.java

rev 48077 : 8193128: Reduce number of implementation classes returned by List/Set/Map.of()
Reviewed-by: smarks

*** 786,796 ****
       * @return an empty {@code List}
       *
       * @since 9
       */
      static <E> List<E> of() {
!         return ImmutableCollections.List0.instance();
      }
  
      /**
       * Returns an unmodifiable list containing one element.
       *
--- 786,796 ----
       * @return an empty {@code List}
       *
       * @since 9
       */
      static <E> List<E> of() {
!         return ImmutableCollections.AbstractImmutableList.emptyList();
      }
  
      /**
       * Returns an unmodifiable list containing one element.
       *
*** 802,812 ****
       * @throws NullPointerException if the element is {@code null}
       *
       * @since 9
       */
      static <E> List<E> of(E e1) {
!         return new ImmutableCollections.List1<>(e1);
      }
  
      /**
       * Returns an unmodifiable list containing two elements.
       *
--- 802,812 ----
       * @throws NullPointerException if the element is {@code null}
       *
       * @since 9
       */
      static <E> List<E> of(E e1) {
!         return ImmutableCollections.AbstractImmutableList.of(e1);
      }
  
      /**
       * Returns an unmodifiable list containing two elements.
       *
*** 819,829 ****
       * @throws NullPointerException if an element is {@code null}
       *
       * @since 9
       */
      static <E> List<E> of(E e1, E e2) {
!         return new ImmutableCollections.List2<>(e1, e2);
      }
  
      /**
       * Returns an unmodifiable list containing three elements.
       *
--- 819,829 ----
       * @throws NullPointerException if an element is {@code null}
       *
       * @since 9
       */
      static <E> List<E> of(E e1, E e2) {
!         return ImmutableCollections.AbstractImmutableList.of(e1, e2);
      }
  
      /**
       * Returns an unmodifiable list containing three elements.
       *
*** 1027,1046 ****
       * @since 9
       */
      @SafeVarargs
      @SuppressWarnings("varargs")
      static <E> List<E> of(E... elements) {
!         switch (elements.length) { // implicit null check of elements
!             case 0:
!                 return ImmutableCollections.List0.instance();
!             case 1:
!                 return new ImmutableCollections.List1<>(elements[0]);
!             case 2:
!                 return new ImmutableCollections.List2<>(elements[0], elements[1]);
!             default:
!                 return new ImmutableCollections.ListN<>(elements);
!         }
      }
  
      /**
       * Returns an <a href="#unmodifiable">unmodifiable List</a> containing the elements of
       * the given Collection, in its iteration order. The given Collection must not be null,
--- 1027,1037 ----
       * @since 9
       */
      @SafeVarargs
      @SuppressWarnings("varargs")
      static <E> List<E> of(E... elements) {
!         return ImmutableCollections.AbstractImmutableList.of(elements);
      }
  
      /**
       * Returns an <a href="#unmodifiable">unmodifiable List</a> containing the elements of
       * the given Collection, in its iteration order. The given Collection must not be null,