< prev index next >
src/java.base/share/classes/java/util/Set.java
Print this page
rev 47479 : 8177290: add copy factory methods for unmodifiable List, Set, Map
8184690: add Collectors for collecting into unmodifiable List, Set, and Map
Reviewed-by: alanb, briangoetz, dholmes, rriggs, scolebourne
@@ -61,19 +61,20 @@
* the insertion of an ineligible element into the set may throw an
* exception or it may succeed, at the option of the implementation.
* Such exceptions are marked as "optional" in the specification for this
* interface.
*
- * <h2><a id="immutable">Immutable Set Static Factory Methods</a></h2>
- * <p>The {@link Set#of(Object...) Set.of()} static factory methods
- * provide a convenient way to create immutable sets. The {@code Set}
+ * <h2><a id="unmodifiable">Unmodifiable Sets</a></h2>
+ * <p>The {@link Set#of(Object...) Set.of} and
+ * {@link Set#copyOf Set.copyOf} static factory methods
+ * provide a convenient way to create unmodifiable sets. The {@code Set}
* instances created by these methods have the following characteristics:
*
* <ul>
- * <li>They are <em>structurally immutable</em>. Elements cannot be added or
- * removed. Calling any mutator method will always cause
- * {@code UnsupportedOperationException} to be thrown.
+ * <li>They are <a href="Collection.html#unmodifiable"><i>unmodifiable</i></a>. Elements cannot
+ * be added or removed. Calling any mutator method on the Set
+ * will always cause {@code UnsupportedOperationException} to be thrown.
* However, if the contained elements are themselves mutable, this may cause the
* Set to behave inconsistently or its contents to appear to change.
* <li>They disallow {@code null} elements. Attempts to create them with
* {@code null} elements result in {@code NullPointerException}.
* <li>They are serializable if all elements are serializable.
@@ -437,12 +438,12 @@
default Spliterator<E> spliterator() {
return Spliterators.spliterator(this, Spliterator.DISTINCT);
}
/**
- * Returns an immutable set containing zero elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing zero elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @return an empty {@code Set}
*
* @since 9
@@ -450,12 +451,12 @@
static <E> Set<E> of() {
return ImmutableCollections.Set0.instance();
}
/**
- * Returns an immutable set containing one element.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing one element.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @param e1 the single element
* @return a {@code Set} containing the specified element
* @throws NullPointerException if the element is {@code null}
@@ -465,12 +466,12 @@
static <E> Set<E> of(E e1) {
return new ImmutableCollections.Set1<>(e1);
}
/**
- * Returns an immutable set containing two elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing two elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @param e1 the first element
* @param e2 the second element
* @return a {@code Set} containing the specified elements
@@ -482,12 +483,12 @@
static <E> Set<E> of(E e1, E e2) {
return new ImmutableCollections.Set2<>(e1, e2);
}
/**
- * Returns an immutable set containing three elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing three elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
@@ -500,12 +501,12 @@
static <E> Set<E> of(E e1, E e2, E e3) {
return new ImmutableCollections.SetN<>(e1, e2, e3);
}
/**
- * Returns an immutable set containing four elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing four elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
@@ -519,12 +520,12 @@
static <E> Set<E> of(E e1, E e2, E e3, E e4) {
return new ImmutableCollections.SetN<>(e1, e2, e3, e4);
}
/**
- * Returns an immutable set containing five elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing five elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
@@ -539,12 +540,12 @@
static <E> Set<E> of(E e1, E e2, E e3, E e4, E e5) {
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5);
}
/**
- * Returns an immutable set containing six elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing six elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
@@ -561,12 +562,12 @@
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5,
e6);
}
/**
- * Returns an immutable set containing seven elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing seven elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
@@ -584,12 +585,12 @@
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5,
e6, e7);
}
/**
- * Returns an immutable set containing eight elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing eight elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
@@ -608,12 +609,12 @@
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5,
e6, e7, e8);
}
/**
- * Returns an immutable set containing nine elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing nine elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
@@ -633,12 +634,12 @@
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5,
e6, e7, e8, e9);
}
/**
- * Returns an immutable set containing ten elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing ten elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @param <E> the {@code Set}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
@@ -659,12 +660,12 @@
return new ImmutableCollections.SetN<>(e1, e2, e3, e4, e5,
e6, e7, e8, e9, e10);
}
/**
- * Returns an immutable set containing an arbitrary number of elements.
- * See <a href="#immutable">Immutable Set Static Factory Methods</a> for details.
+ * Returns an unmodifiable set containing an arbitrary number of elements.
+ * See <a href="#unmodifiable">Unmodifiable Sets</a> for details.
*
* @apiNote
* This method also accepts a single array as an argument. The element type of
* the resulting set will be the component type of the array, and the size of
* the set will be equal to the length of the array. To create a set with
@@ -698,6 +699,28 @@
return new ImmutableCollections.Set2<>(elements[0], elements[1]);
default:
return new ImmutableCollections.SetN<>(elements);
}
}
+
+ /**
+ * Returns an <a href="#unmodifiable">unmodifiable Set</a> containing the elements
+ * of the given Collection. The given Collection must not be null, and it must not
+ * contain any null elements. If the given Collection contains duplicate elements,
+ * an arbitrary element of the duplicates is preserved. If the given Collection is
+ * subsequently modified, the returned Set will not reflect such modifications.
+ *
+ * @param <E> the {@code Set}'s element type
+ * @param coll the collection from which elements are drawn, must be non-null
+ * @return the new {@code Set}
+ * @throws NullPointerException if coll is null, or if it contains any nulls
+ * @since 10
+ */
+ @SuppressWarnings("unchecked")
+ static <E> Set<E> copyOf(Collection<? extends E> coll) {
+ if (coll instanceof ImmutableCollections.AbstractImmutableSet) {
+ return (Set<E>)coll;
+ } else {
+ return (Set<E>)Set.of(coll.stream().distinct().toArray());
+ }
+ }
}
< prev index next >