default boolean removeIf(Predicate<? super E> filter) {
Objects.requireNonNull(filter);
boolean removed = false;
final Iterator<E> each = iterator();
while (each.hasNext()) {
if (filter.test(each.next())) {
each.remove();
removed = true;
}
}
return removed;
}
default Spliterator<E> spliterator() {
return Spliterators.spliterator(this, 0);
}
default Stream<E> stream() {
return StreamSupport.stream(spliterator(), false);
}
default Stream<E> parallelStream() {
return StreamSupport.stream(spliterator(), true);
}
package java.util;
import java.util.function.Predicate;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* The root interface in the <i>collection hierarchy</i>. A collection
* represents a group of objects, known as its <i>elements</i>. Some
* collections allow duplicate elements and others do not. Some are ordered
* and others unordered. The JDK does not provide any <i>direct</i>
* implementations of this interface: it provides implementations of more
* specific subinterfaces like {@code Set} and {@code List}. This interface
* is typically used to pass collections around and manipulate them where
* maximum generality is desired.
*
* <p><i>Bags</i> or <i>multisets</i> (unordered collections that may contain
* duplicate elements) should implement this interface directly.
*
* <p>All general-purpose {@code Collection} implementation classes (which
* typically implement {@code Collection} indirectly through one of its
* subinterfaces) should provide two "standard" constructors: a void (no
* arguments) constructor, which creates an empty collection, and a
* constructor with a single argument of type {@code Collection}, which
* creates a new collection with the same elements as its argument. In
* effect, the latter constructor allows the user to copy any collection,
* producing an equivalent collection of the desired implementation type.
* There is no way to enforce this convention (as interfaces cannot contain
* constructors) but all of the general-purpose {@code Collection}
* implementations in the Java platform libraries comply.
*
* <p>Certain methods are specified to be
* <i>optional</i>. If a collection implementation doesn't implement a
* particular operation, it should define the corresponding method to throw
* {@code UnsupportedOperationException}. Such methods are marked "optional
* operation" in method specifications of the collections interfaces.
*
* <p><a id="optional-restrictions"></a>Some collection implementations
* have restrictions on the elements that they may contain.
* For example, some implementations prohibit null elements,
* and some have restrictions on the types of their elements. Attempting to
* add an ineligible element throws an unchecked exception, typically
* {@code NullPointerException} or {@code ClassCastException}. Attempting
* to query the presence of an ineligible element may throw an exception,
* or it may simply return false; some implementations will exhibit the former
* behavior and some will exhibit the latter. More generally, attempting an
* operation on an ineligible element whose completion would not result in
* the insertion of an ineligible element into the collection 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.
*
* <p>It is up to each collection to determine its own synchronization
* policy. In the absence of a stronger guarantee by the
* implementation, undefined behavior may result from the invocation
* of any method on a collection that is being mutated by another
* thread; this includes direct invocations, passing the collection to
* a method that might perform invocations, and using an existing
* iterator to examine the collection.
*
* <p>Many methods in Collections Framework interfaces are defined in
* terms of the {@link Object#equals(Object) equals} method. For example,
* the specification for the {@link #contains(Object) contains(Object o)}
* method says: "returns {@code true} if and only if this collection
* contains at least one element {@code e} such that
* {@code (o==null ? e==null : o.equals(e))}." This specification should
* <i>not</i> be construed to imply that invoking {@code Collection.contains}
* with a non-null argument {@code o} will cause {@code o.equals(e)} to be
* invoked for any element {@code e}. Implementations are free to implement
* optimizations whereby the {@code equals} invocation is avoided, for
* example, by first comparing the hash codes of the two elements. (The
* {@link Object#hashCode()} specification guarantees that two objects with
* unequal hash codes cannot be equal.) More generally, implementations of
* the various Collections Framework interfaces are free to take advantage of
* the specified behavior of underlying {@link Object} methods wherever the
* implementor deems it appropriate.
*
* <p>Some collection operations which perform recursive traversal of the
* collection may fail with an exception for self-referential instances where
* the collection directly or indirectly contains itself. This includes the
* {@code clone()}, {@code equals()}, {@code hashCode()} and {@code toString()}
* methods. Implementations may optionally handle the self-referential scenario,
* however most current implementations do not do so.
*
* <h2><a id="view">View Collections</a></h2>
*
* <p>Most collections manage storage for elements they contain. By contrast, <i>view
* collections</i> themselves do not store elements, but instead they rely on a
* backing collection to store the actual elements. Operations that are not handled
* by the view collection itself are delegated to the backing collection. Examples of
* view collections include the wrapper collections returned by methods such as
* {@link Collections#checkedCollection Collections.checkedCollection},
* {@link Collections#synchronizedCollection Collections.synchronizedCollection}, and
* {@link Collections#unmodifiableCollection Collections.unmodifiableCollection}.
* Other examples of view collections include collections that provide a
* different representation of the same elements, for example, as
* provided by {@link List#subList List.subList},
* {@link NavigableSet#subSet NavigableSet.subSet}, or
* {@link Map#entrySet Map.entrySet}.
* Any changes made to the backing collection are visible in the view collection.
* Correspondingly, any changes made to the view collection — if changes
* are permitted — are written through to the backing collection.
* Although they technically aren't collections, instances of
* {@link Iterator} and {@link ListIterator} can also allow modifications
* to be written through to the backing collection, and in some cases,
* modifications to the backing collection will be visible to the Iterator
* during iteration.
*
* <h2><a id="unmodifiable">Unmodifiable Collections</a></h2>
*
* <p>Certain methods of this interface are considered "destructive" and are called
* "mutator" methods in that they modify the group of objects contained within
* the collection on which they operate. They can be specified to throw
* {@code UnsupportedOperationException} if this collection implementation
* does not support the operation. Such methods should (but are not required
* to) throw an {@code UnsupportedOperationException} if the invocation would
* have no effect on the collection. For example, consider a collection that
* does not support the {@link #add add} operation. What will happen if the
* {@link #addAll addAll} method is invoked on this collection, with an empty
* collection as the argument? The addition of zero elements has no effect,
* so it is permissible for this collection simply to do nothing and not to throw
* an exception. However, it is recommended that such cases throw an exception
* unconditionally, as throwing only in certain cases can lead to
* programming errors.
*
* <p>An <i>unmodifiable collection</i> is a collection, all of whose
* mutator methods (as defined above) are specified to throw
* {@code UnsupportedOperationException}. Such a collection thus cannot be
* modified by calling any methods on it. For a collection to be properly
* unmodifiable, any view collections derived from it must also be unmodifiable.
* For example, if a List is unmodifiable, the List returned by
* {@link List#subList List.subList} is also unmodifiable.
*
* <p>An unmodifiable collection is not necessarily immutable. If the
* contained elements are mutable, the entire collection is clearly
* mutable, even though it might be unmodifiable. For example, consider
* two unmodifiable lists containing mutable elements. The result of calling
* {@code list1.equals(list2)} might differ from one call to the next if
* the elements had been mutated, even though both lists are unmodifiable.
* However, if an unmodifiable collection contains all immutable elements,
* it can be considered effectively immutable.
*
* <h2><a id="unmodview">Unmodifiable View Collections</a></h2>
*
* <p>An <i>unmodifiable view collection</i> is a collection that is unmodifiable
* and that is also a view onto a backing collection. Its mutator methods throw
* {@code UnsupportedOperationException}, as described above, while
* reading and querying methods are delegated to the backing collection.
* The effect is to provide read-only access to the backing collection.
* This is useful for a component to provide users with read access to
* an internal collection, while preventing them from modifying such
* collections unexpectedly. Examples of unmodifiable view collections
* are those returned by the
* {@link Collections#unmodifiableCollection Collections.unmodifiableCollection},
* {@link Collections#unmodifiableList Collections.unmodifiableList}, and
* related methods.
*
* <p>Note that changes to the backing collection might still be possible,
* and if they occur, they are visible through the unmodifiable view. Thus,
* an unmodifiable view collection is not necessarily immutable. However,
* if the backing collection of an unmodifiable view is effectively immutable,
* or if the only reference to the backing collection is through an
* unmodifiable view, the view can be considered effectively immutable.
*
* <p>This interface is a member of the
* <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
* Java Collections Framework</a>.
*
* @implSpec
* The default method implementations (inherited or otherwise) do not apply any
* synchronization protocol. If a {@code Collection} implementation has a
* specific synchronization protocol, then it must override default
* implementations to apply that protocol.
*
* @param <E> the type of elements in this collection
*
* @author Josh Bloch
* @author Neal Gafter
* @see Set
* @see List
* @see Map
* @see SortedSet
* @see SortedMap
* @see HashSet
* @see TreeSet
* @see ArrayList
* @see LinkedList
* @see Vector
* @see Collections
* @see Arrays
* @see AbstractCollection
* @since 1.2
*/
public interface Collection<E> extends Iterable<E> {
// Query Operations
/**
* Returns the number of elements in this collection. If this collection
* contains more than {@code Integer.MAX_VALUE} elements, returns
* {@code Integer.MAX_VALUE}.
*
* @return the number of elements in this collection
*/
int size();
/**
* Returns {@code true} if this collection contains no elements.
*
* @return {@code true} if this collection contains no elements
*/
boolean isEmpty();
/**
* Returns {@code true} if this collection contains the specified element.
* More formally, returns {@code true} if and only if this collection
* contains at least one element {@code e} such that
* {@code Objects.equals(o, e)}.
*
* @param o element whose presence in this collection is to be tested
* @return {@code true} if this collection contains the specified
* element
* @throws ClassCastException if the type of the specified element
* is incompatible with this collection
* (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified element is null and this
* collection does not permit null elements
* (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
*/
boolean contains(Object o);
/**
* Returns an iterator over the elements in this collection. There are no
* guarantees concerning the order in which the elements are returned
* (unless this collection is an instance of some class that provides a
* guarantee).
*
* @return an {@code Iterator} over the elements in this collection
*/
Iterator<E> iterator();
/**
* Returns an array containing all of the elements in this collection.
* If this collection makes any guarantees as to what order its elements
* are returned by its iterator, this method must return the elements in
* the same order. The returned array's {@linkplain Class#getComponentType
* runtime component type} is {@code Object}.
*
* <p>The returned array will be "safe" in that no references to it are
* maintained by this collection. (In other words, this method must
* allocate a new array even if this collection is backed by an array).
* The caller is thus free to modify the returned array.
*
* <p>This method acts as bridge between array-based and collection-based
* APIs.
*
* @return an array, whose {@linkplain Class#getComponentType runtime component
* type} is {@code Object}, containing all of the elements in this collection
*/
Object[] toArray();
/**
* Returns an array containing all of the elements in this collection;
* the runtime type of the returned array is that of the specified array.
* If the collection fits in the specified array, it is returned therein.
* Otherwise, a new array is allocated with the runtime type of the
* specified array and the size of this collection.
*
* <p>If this collection fits in the specified array with room to spare
* (i.e., the array has more elements than this collection), the element
* in the array immediately following the end of the collection is set to
* {@code null}. (This is useful in determining the length of this
* collection <i>only</i> if the caller knows that this collection does
* not contain any {@code null} elements.)
*
* <p>If this collection makes any guarantees as to what order its elements
* are returned by its iterator, this method must return the elements in
* the same order.
*
* <p>Like the {@link #toArray()} method, this method acts as bridge between
* array-based and collection-based APIs. Further, this method allows
* precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs.
*
* <p>Suppose {@code x} is a collection known to contain only strings.
* The following code can be used to dump the collection into a newly
* allocated array of {@code String}:
*
* <pre>
* String[] y = x.toArray(new String[0]);</pre>
*
* Note that {@code toArray(new Object[0])} is identical in function to
* {@code toArray()}.
*
* @param <T> the component type of the array to contain the collection
* @param a the array into which the elements of this collection are to be
* stored, if it is big enough; otherwise, a new array of the same
* runtime type is allocated for this purpose.
* @return an array containing all of the elements in this collection
* @throws ArrayStoreException if the runtime type of any element in this
* collection is not assignable to the {@linkplain Class#getComponentType
* runtime component type} of the specified array
* @throws NullPointerException if the specified array is null
*/
<T> T[] toArray(T[] a);
// Modification Operations
/**
* Ensures that this collection contains the specified element (optional
* operation). Returns {@code true} if this collection changed as a
* result of the call. (Returns {@code false} if this collection does
* not permit duplicates and already contains the specified element.)<p>
*
* Collections that support this operation may place limitations on what
* elements may be added to this collection. In particular, some
* collections will refuse to add {@code null} elements, and others will
* impose restrictions on the type of elements that may be added.
* Collection classes should clearly specify in their documentation any
* restrictions on what elements may be added.<p>
*
* If a collection refuses to add a particular element for any reason
* other than that it already contains the element, it <i>must</i> throw
* an exception (rather than returning {@code false}). This preserves
* the invariant that a collection always contains the specified element
* after this call returns.
*
* @param e element whose presence in this collection is to be ensured
* @return {@code true} if this collection changed as a result of the
* call
* @throws UnsupportedOperationException if the {@code add} operation
* is not supported by this collection
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this collection
* @throws NullPointerException if the specified element is null and this
* collection does not permit null elements
* @throws IllegalArgumentException if some property of the element
* prevents it from being added to this collection
* @throws IllegalStateException if the element cannot be added at this
* time due to insertion restrictions
*/
boolean add(E e);
/**
* Removes a single instance of the specified element from this
* collection, if it is present (optional operation). More formally,
* removes an element {@code e} such that
* {@code Objects.equals(o, e)}, if
* this collection contains one or more such elements. Returns
* {@code true} if this collection contained the specified element (or
* equivalently, if this collection changed as a result of the call).
*
* @param o element to be removed from this collection, if present
* @return {@code true} if an element was removed as a result of this call
* @throws ClassCastException if the type of the specified element
* is incompatible with this collection
* (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified element is null and this
* collection does not permit null elements
* (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
* @throws UnsupportedOperationException if the {@code remove} operation
* is not supported by this collection
*/
boolean remove(Object o);
// Bulk Operations
/**
* Returns {@code true} if this collection contains all of the elements
* in the specified collection.
*
* @param c collection to be checked for containment in this collection
* @return {@code true} if this collection contains all of the elements
* in the specified collection
* @throws ClassCastException if the types of one or more elements
* in the specified collection are incompatible with this
* collection
* (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified collection contains one
* or more null elements and this collection does not permit null
* elements
* (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>),
* or if the specified collection is null.
* @see #contains(Object)
*/
boolean containsAll(Collection<?> c);
/**
* Adds all of the elements in the specified collection to this collection
* (optional operation). The behavior of this operation is undefined if
* the specified collection is modified while the operation is in progress.
* (This implies that the behavior of this call is undefined if the
* specified collection is this collection, and this collection is
* nonempty.)
*
* @param c collection containing elements to be added to this collection
* @return {@code true} if this collection changed as a result of the call
* @throws UnsupportedOperationException if the {@code addAll} operation
* is not supported by this collection
* @throws ClassCastException if the class of an element of the specified
* collection prevents it from being added to this collection
* @throws NullPointerException if the specified collection contains a
* null element and this collection does not permit null elements,
* or if the specified collection is null
* @throws IllegalArgumentException if some property of an element of the
* specified collection prevents it from being added to this
* collection
* @throws IllegalStateException if not all the elements can be added at
* this time due to insertion restrictions
* @see #add(Object)
*/
boolean addAll(Collection<? extends E> c);
/**
* Removes all of this collection's elements that are also contained in the
* specified collection (optional operation). After this call returns,
* this collection will contain no elements in common with the specified
* collection.
*
* @param c collection containing elements to be removed from this collection
* @return {@code true} if this collection changed as a result of the
* call
* @throws UnsupportedOperationException if the {@code removeAll} method
* is not supported by this collection
* @throws ClassCastException if the types of one or more elements
* in this collection are incompatible with the specified
* collection
* (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if this collection contains one or more
* null elements and the specified collection does not support
* null elements
* (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>),
* or if the specified collection is null
* @see #remove(Object)
* @see #contains(Object)
*/
boolean removeAll(Collection<?> c);
/**
* Removes all of the elements of this collection that satisfy the given
* predicate. Errors or runtime exceptions thrown during iteration or by
* the predicate are relayed to the caller.
*
* @implSpec
* The default implementation traverses all elements of the collection using
* its {@link #iterator}. Each matching element is removed using
* {@link Iterator#remove()}. If the collection's iterator does not
* support removal then an {@code UnsupportedOperationException} will be
* thrown on the first matching element.
*
* @param filter a predicate which returns {@code true} for elements to be
* removed
* @return {@code true} if any elements were removed
* @throws NullPointerException if the specified filter is null
* @throws UnsupportedOperationException if elements cannot be removed
* from this collection. Implementations may throw this exception if a
* matching element cannot be removed or if, in general, removal is not
* supported.
* @since 1.8
*/
default boolean removeIf(Predicate<? super E> filter) {
Objects.requireNonNull(filter);
boolean removed = false;
final Iterator<E> each = iterator();
while (each.hasNext()) {
if (filter.test(each.next())) {
each.remove();
removed = true;
}
}
return removed;
}
/**
* Retains only the elements in this collection that are contained in the
* specified collection (optional operation). In other words, removes from
* this collection all of its elements that are not contained in the
* specified collection.
*
* @param c collection containing elements to be retained in this collection
* @return {@code true} if this collection changed as a result of the call
* @throws UnsupportedOperationException if the {@code retainAll} operation
* is not supported by this collection
* @throws ClassCastException if the types of one or more elements
* in this collection are incompatible with the specified
* collection
* (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if this collection contains one or more
* null elements and the specified collection does not permit null
* elements
* (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>),
* or if the specified collection is null
* @see #remove(Object)
* @see #contains(Object)
*/
boolean retainAll(Collection<?> c);
/**
* Removes all of the elements from this collection (optional operation).
* The collection will be empty after this method returns.
*
* @throws UnsupportedOperationException if the {@code clear} operation
* is not supported by this collection
*/
void clear();
// Comparison and hashing
/**
* Compares the specified object with this collection for equality. <p>
*
* While the {@code Collection} interface adds no stipulations to the
* general contract for the {@code Object.equals}, programmers who
* implement the {@code Collection} interface "directly" (in other words,
* create a class that is a {@code Collection} but is not a {@code Set}
* or a {@code List}) must exercise care if they choose to override the
* {@code Object.equals}. It is not necessary to do so, and the simplest
* course of action is to rely on {@code Object}'s implementation, but
* the implementor may wish to implement a "value comparison" in place of
* the default "reference comparison." (The {@code List} and
* {@code Set} interfaces mandate such value comparisons.)<p>
*
* The general contract for the {@code Object.equals} method states that
* equals must be symmetric (in other words, {@code a.equals(b)} if and
* only if {@code b.equals(a)}). The contracts for {@code List.equals}
* and {@code Set.equals} state that lists are only equal to other lists,
* and sets to other sets. Thus, a custom {@code equals} method for a
* collection class that implements neither the {@code List} nor
* {@code Set} interface must return {@code false} when this collection
* is compared to any list or set. (By the same logic, it is not possible
* to write a class that correctly implements both the {@code Set} and
* {@code List} interfaces.)
*
* @param o object to be compared for equality with this collection
* @return {@code true} if the specified object is equal to this
* collection
*
* @see Object#equals(Object)
* @see Set#equals(Object)
* @see List#equals(Object)
*/
boolean equals(Object o);
/**
* Returns the hash code value for this collection. While the
* {@code Collection} interface adds no stipulations to the general
* contract for the {@code Object.hashCode} method, programmers should
* take note that any class that overrides the {@code Object.equals}
* method must also override the {@code Object.hashCode} method in order
* to satisfy the general contract for the {@code Object.hashCode} method.
* In particular, {@code c1.equals(c2)} implies that
* {@code c1.hashCode()==c2.hashCode()}.
*
* @return the hash code value for this collection
*
* @see Object#hashCode()
* @see Object#equals(Object)
*/
int hashCode();
/**
* Creates a {@link Spliterator} over the elements in this collection.
*
* Implementations should document characteristic values reported by the
* spliterator. Such characteristic values are not required to be reported
* if the spliterator reports {@link Spliterator#SIZED} and this collection
* contains no elements.
*
* <p>The default implementation should be overridden by subclasses that
* can return a more efficient spliterator. In order to
* preserve expected laziness behavior for the {@link #stream()} and
* {@link #parallelStream()} methods, spliterators should either have the
* characteristic of {@code IMMUTABLE} or {@code CONCURRENT}, or be
* <em><a href="Spliterator.html#binding">late-binding</a></em>.
* If none of these is practical, the overriding class should describe the
* spliterator's documented policy of binding and structural interference,
* and should override the {@link #stream()} and {@link #parallelStream()}
* methods to create streams using a {@code Supplier} of the spliterator,
* as in:
* <pre>{@code
* Stream<E> s = StreamSupport.stream(() -> spliterator(), spliteratorCharacteristics)
* }</pre>
* <p>These requirements ensure that streams produced by the
* {@link #stream()} and {@link #parallelStream()} methods will reflect the
* contents of the collection as of initiation of the terminal stream
* operation.
*
* @implSpec
* The default implementation creates a
* <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator
* from the collection's {@code Iterator}. The spliterator inherits the
* <em>fail-fast</em> properties of the collection's iterator.
* <p>
* The created {@code Spliterator} reports {@link Spliterator#SIZED}.
*
* @implNote
* The created {@code Spliterator} additionally reports
* {@link Spliterator#SUBSIZED}.
*
* <p>If a spliterator covers no elements then the reporting of additional
* characteristic values, beyond that of {@code SIZED} and {@code SUBSIZED},
* does not aid clients to control, specialize or simplify computation.
* However, this does enable shared use of an immutable and empty
* spliterator instance (see {@link Spliterators#emptySpliterator()}) for
* empty collections, and enables clients to determine if such a spliterator
* covers no elements.
*
* @return a {@code Spliterator} over the elements in this collection
* @since 1.8
*/
@Override
default Spliterator<E> spliterator() {
return Spliterators.spliterator(this, 0);
}
/**
* Returns a sequential {@code Stream} with this collection as its source.
*
* <p>This method should be overridden when the {@link #spliterator()}
* method cannot return a spliterator that is {@code IMMUTABLE},
* {@code CONCURRENT}, or <em>late-binding</em>. (See {@link #spliterator()}
* for details.)
*
* @implSpec
* The default implementation creates a sequential {@code Stream} from the
* collection's {@code Spliterator}.
*
* @return a sequential {@code Stream} over the elements in this collection
* @since 1.8
*/
default Stream<E> stream() {
return StreamSupport.stream(spliterator(), false);
}
/**
* Returns a possibly parallel {@code Stream} with this collection as its
* source. It is allowable for this method to return a sequential stream.
*
* <p>This method should be overridden when the {@link #spliterator()}
* method cannot return a spliterator that is {@code IMMUTABLE},
* {@code CONCURRENT}, or <em>late-binding</em>. (See {@link #spliterator()}
* for details.)
*
* @implSpec
* The default implementation creates a parallel {@code Stream} from the
* collection's {@code Spliterator}.
*
* @return a possibly parallel {@code Stream} over the elements in this
* collection
* @since 1.8
*/
default Stream<E> parallelStream() {
return StreamSupport.stream(spliterator(), true);
}
}
It inherits the Collection.
package java.util;
import java.util.function.UnaryOperator;
/**
* An ordered collection (also known as a <i>sequence</i>). The user of this
* interface has precise control over where in the list each element is
* inserted. The user can access elements by their integer index (position in
* the list), and search for elements in the list.<p>
*
* Unlike sets, lists typically allow duplicate elements. More formally,
* lists typically allow pairs of elements {@code e1} and {@code e2}
* such that {@code e1.equals(e2)}, and they typically allow multiple
* null elements if they allow null elements at all. It is not inconceivable
* that someone might wish to implement a list that prohibits duplicates, by
* throwing runtime exceptions when the user attempts to insert them, but we
* expect this usage to be rare.<p>
*
* The {@code List} interface places additional stipulations, beyond those
* specified in the {@code Collection} interface, on the contracts of the
* {@code iterator}, {@code add}, {@code remove}, {@code equals}, and
* {@code hashCode} methods. Declarations for other inherited methods are
* also included here for convenience.<p>
*
* The {@code List} interface provides four methods for positional (indexed)
* access to list elements. Lists (like Java arrays) are zero based. Note
* that these operations may execute in time proportional to the index value
* for some implementations (the {@code LinkedList} class, for
* example). Thus, iterating over the elements in a list is typically
* preferable to indexing through it if the caller does not know the
* implementation.<p>
*
* The {@code List} interface provides a special iterator, called a
* {@code ListIterator}, that allows element insertion and replacement, and
* bidirectional access in addition to the normal operations that the
* {@code Iterator} interface provides. A method is provided to obtain a
* list iterator that starts at a specified position in the list.<p>
*
* The {@code List} interface provides two methods to search for a specified
* object. From a performance standpoint, these methods should be used with
* caution. In many implementations they will perform costly linear
* searches.<p>
*
* The {@code List} interface provides two methods to efficiently insert and
* remove multiple elements at an arbitrary point in the list.<p>
*
* Note: While it is permissible for lists to contain themselves as elements,
* extreme caution is advised: the {@code equals} and {@code hashCode}
* methods are no longer well defined on such a list.
*
* <p>Some list implementations have restrictions on the elements that
* they may contain. For example, some implementations prohibit null elements,
* and some have restrictions on the types of their elements. Attempting to
* add an ineligible element throws an unchecked exception, typically
* {@code NullPointerException} or {@code ClassCastException}. Attempting
* to query the presence of an ineligible element may throw an exception,
* or it may simply return false; some implementations will exhibit the former
* behavior and some will exhibit the latter. More generally, attempting an
* operation on an ineligible element whose completion would not result in
* the insertion of an ineligible element into the list 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="unmodifiable">Unmodifiable Lists</a></h2>
* <p>The {@link List#of(Object...) List.of} and
* {@link List#copyOf List.copyOf} static factory methods
* provide a convenient way to create unmodifiable lists. The {@code List}
* instances created by these methods have the following characteristics:
*
* <ul>
* <li>They are <a href="Collection.html#unmodifiable"><i>unmodifiable</i></a>. Elements cannot
* be added, removed, or replaced. Calling any mutator method on the List
* will always cause {@code UnsupportedOperationException} to be thrown.
* However, if the contained elements are themselves mutable,
* this may cause the List's 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.
* <li>The order of elements in the list is the same as the order of the
* provided arguments, or of the elements in the provided array.
* <li>They are <a href="../lang/doc-files/ValueBased.html">value-based</a>.
* Callers should make no assumptions about the identity of the returned instances.
* Factories are free to create new instances or reuse existing ones. Therefore,
* identity-sensitive operations on these instances (reference equality ({@code ==}),
* identity hash code, and synchronization) are unreliable and should be avoided.
* <li>They are serialized as specified on the
* <a href="{@docRoot}/serialized-form.html#java.util.CollSer">Serialized Form</a>
* page.
* </ul>
*
* <p>This interface is a member of the
* <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
* Java Collections Framework</a>.
*
* @param <E> the type of elements in this list
*
* @author Josh Bloch
* @author Neal Gafter
* @see Collection
* @see Set
* @see ArrayList
* @see LinkedList
* @see Vector
* @see Arrays#asList(Object[])
* @see Collections#nCopies(int, Object)
* @see Collections#EMPTY_LIST
* @see AbstractList
* @see AbstractSequentialList
* @since 1.2
*/
public interface List<E> extends Collection<E> {
// Query Operations
/**
* Returns the number of elements in this list. If this list contains
* more than {@code Integer.MAX_VALUE} elements, returns
* {@code Integer.MAX_VALUE}.
*
* @return the number of elements in this list
*/
int size();
/**
* Returns {@code true} if this list contains no elements.
*
* @return {@code true} if this list contains no elements
*/
boolean isEmpty();
/**
* Returns {@code true} if this list contains the specified element.
* More formally, returns {@code true} if and only if this list contains
* at least one element {@code e} such that
* {@code Objects.equals(o, e)}.
*
* @param o element whose presence in this list is to be tested
* @return {@code true} if this list contains the specified element
* @throws ClassCastException if the type of the specified element
* is incompatible with this list
* (<a href="Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified element is null and this
* list does not permit null elements
* (<a href="Collection.html#optional-restrictions">optional</a>)
*/
boolean contains(Object o);
/**
* Returns an iterator over the elements in this list in proper sequence.
*
* @return an iterator over the elements in this list in proper sequence
*/
Iterator<E> iterator();
/**
* Returns an array containing all of the elements in this list in proper
* sequence (from first to last element).
*
* <p>The returned array will be "safe" in that no references to it are
* maintained by this list. (In other words, this method must
* allocate a new array even if this list is backed by an array).
* The caller is thus free to modify the returned array.
*
* <p>This method acts as bridge between array-based and collection-based
* APIs.
*
* @return an array containing all of the elements in this list in proper
* sequence
* @see Arrays#asList(Object[])
*/
Object[] toArray();
/**
* Returns an array containing all of the elements in this list in
* proper sequence (from first to last element); the runtime type of
* the returned array is that of the specified array. If the list fits
* in the specified array, it is returned therein. Otherwise, a new
* array is allocated with the runtime type of the specified array and
* the size of this list.
*
* <p>If the list fits in the specified array with room to spare (i.e.,
* the array has more elements than the list), the element in the array
* immediately following the end of the list is set to {@code null}.
* (This is useful in determining the length of the list <i>only</i> if
* the caller knows that the list does not contain any null elements.)
*
* <p>Like the {@link #toArray()} method, this method acts as bridge between
* array-based and collection-based APIs. Further, this method allows
* precise control over the runtime type of the output array, and may,
* under certain circumstances, be used to save allocation costs.
*
* <p>Suppose {@code x} is a list known to contain only strings.
* The following code can be used to dump the list into a newly
* allocated array of {@code String}:
*
* <pre>{@code
* String[] y = x.toArray(new String[0]);
* }</pre>
*
* Note that {@code toArray(new Object[0])} is identical in function to
* {@code toArray()}.
*
* @param a the array into which the elements of this list are to
* be stored, if it is big enough; otherwise, a new array of the
* same runtime type is allocated for this purpose.
* @return an array containing the elements of this list
* @throws ArrayStoreException if the runtime type of the specified array
* is not a supertype of the runtime type of every element in
* this list
* @throws NullPointerException if the specified array is null
*/
<T> T[] toArray(T[] a);
// Modification Operations
/**
* Appends the specified element to the end of this list (optional
* operation).
*
* <p>Lists that support this operation may place limitations on what
* elements may be added to this list. In particular, some
* lists will refuse to add null elements, and others will impose
* restrictions on the type of elements that may be added. List
* classes should clearly specify in their documentation any restrictions
* on what elements may be added.
*
* @param e element to be appended to this list
* @return {@code true} (as specified by {@link Collection#add})
* @throws UnsupportedOperationException if the {@code add} operation
* is not supported by this list
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this list
* @throws NullPointerException if the specified element is null and this
* list does not permit null elements
* @throws IllegalArgumentException if some property of this element
* prevents it from being added to this list
*/
boolean add(E e);
/**
* Removes the first occurrence of the specified element from this list,
* if it is present (optional operation). If this list does not contain
* the element, it is unchanged. More formally, removes the element with
* the lowest index {@code i} such that
* {@code Objects.equals(o, get(i))}
* (if such an element exists). Returns {@code true} if this list
* contained the specified element (or equivalently, if this list changed
* as a result of the call).
*
* @param o element to be removed from this list, if present
* @return {@code true} if this list contained the specified element
* @throws ClassCastException if the type of the specified element
* is incompatible with this list
* (<a href="Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified element is null and this
* list does not permit null elements
* (<a href="Collection.html#optional-restrictions">optional</a>)
* @throws UnsupportedOperationException if the {@code remove} operation
* is not supported by this list
*/
boolean remove(Object o);
// Bulk Modification Operations
/**
* Returns {@code true} if this list contains all of the elements of the
* specified collection.
*
* @param c collection to be checked for containment in this list
* @return {@code true} if this list contains all of the elements of the
* specified collection
* @throws ClassCastException if the types of one or more elements
* in the specified collection are incompatible with this
* list
* (<a href="Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified collection contains one
* or more null elements and this list does not permit null
* elements
* (<a href="Collection.html#optional-restrictions">optional</a>),
* or if the specified collection is null
* @see #contains(Object)
*/
boolean containsAll(Collection<?> c);
/**
* Appends all of the elements in the specified collection to the end of
* this list, in the order that they are returned by the specified
* collection's iterator (optional operation). The behavior of this
* operation is undefined if the specified collection is modified while
* the operation is in progress. (Note that this will occur if the
* specified collection is this list, and it's nonempty.)
*
* @param c collection containing elements to be added to this list
* @return {@code true} if this list changed as a result of the call
* @throws UnsupportedOperationException if the {@code addAll} operation
* is not supported by this list
* @throws ClassCastException if the class of an element of the specified
* collection prevents it from being added to this list
* @throws NullPointerException if the specified collection contains one
* or more null elements and this list does not permit null
* elements, or if the specified collection is null
* @throws IllegalArgumentException if some property of an element of the
* specified collection prevents it from being added to this list
* @see #add(Object)
*/
boolean addAll(Collection<? extends E> c);
/**
* Inserts all of the elements in the specified collection into this
* list at the specified position (optional operation). Shifts the
* element currently at that position (if any) and any subsequent
* elements to the right (increases their indices). The new elements
* will appear in this list in the order that they are returned by the
* specified collection's iterator. The behavior of this operation is
* undefined if the specified collection is modified while the
* operation is in progress. (Note that this will occur if the specified
* collection is this list, and it's nonempty.)
*
* @param index index at which to insert the first element from the
* specified collection
* @param c collection containing elements to be added to this list
* @return {@code true} if this list changed as a result of the call
* @throws UnsupportedOperationException if the {@code addAll} operation
* is not supported by this list
* @throws ClassCastException if the class of an element of the specified
* collection prevents it from being added to this list
* @throws NullPointerException if the specified collection contains one
* or more null elements and this list does not permit null
* elements, or if the specified collection is null
* @throws IllegalArgumentException if some property of an element of the
* specified collection prevents it from being added to this list
* @throws IndexOutOfBoundsException if the index is out of range
* ({@code index < 0 || index > size()})
*/
boolean addAll(int index, Collection<? extends E> c);
/**
* Removes from this list all of its elements that are contained in the
* specified collection (optional operation).
*
* @param c collection containing elements to be removed from this list
* @return {@code true} if this list changed as a result of the call
* @throws UnsupportedOperationException if the {@code removeAll} operation
* is not supported by this list
* @throws ClassCastException if the class of an element of this list
* is incompatible with the specified collection
* (<a href="Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if this list contains a null element and the
* specified collection does not permit null elements
* (<a href="Collection.html#optional-restrictions">optional</a>),
* or if the specified collection is null
* @see #remove(Object)
* @see #contains(Object)
*/
boolean removeAll(Collection<?> c);
/**
* Retains only the elements in this list that are contained in the
* specified collection (optional operation). In other words, removes
* from this list all of its elements that are not contained in the
* specified collection.
*
* @param c collection containing elements to be retained in this list
* @return {@code true} if this list changed as a result of the call
* @throws UnsupportedOperationException if the {@code retainAll} operation
* is not supported by this list
* @throws ClassCastException if the class of an element of this list
* is incompatible with the specified collection
* (<a href="Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if this list contains a null element and the
* specified collection does not permit null elements
* (<a href="Collection.html#optional-restrictions">optional</a>),
* or if the specified collection is null
* @see #remove(Object)
* @see #contains(Object)
*/
boolean retainAll(Collection<?> c);
/**
* Replaces each element of this list with the result of applying the
* operator to that element. Errors or runtime exceptions thrown by
* the operator are relayed to the caller.
*
* @implSpec
* The default implementation is equivalent to, for this {@code list}:
* <pre>{@code
* final ListIterator<E> li = list.listIterator();
* while (li.hasNext()) {
* li.set(operator.apply(li.next()));
* }
* }</pre>
*
* If the list's list-iterator does not support the {@code set} operation
* then an {@code UnsupportedOperationException} will be thrown when
* replacing the first element.
*
* @param operator the operator to apply to each element
* @throws UnsupportedOperationException if this list is unmodifiable.
* Implementations may throw this exception if an element
* cannot be replaced or if, in general, modification is not
* supported
* @throws NullPointerException if the specified operator is null or
* if the operator result is a null value and this list does
* not permit null elements
* (<a href="Collection.html#optional-restrictions">optional</a>)
* @since 1.8
*/
default void replaceAll(UnaryOperator<E> operator) {
Objects.requireNonNull(operator);
final ListIterator<E> li = this.listIterator();
while (li.hasNext()) {
li.set(operator.apply(li.next()));
}
}
/**
* Sorts this list according to the order induced by the specified
* {@link Comparator}. The sort is <i>stable</i>: this method must not
* reorder equal elements.
*
* <p>All elements in this list must be <i>mutually comparable</i> using the
* specified comparator (that is, {@code c.compare(e1, e2)} must not throw
* a {@code ClassCastException} for any elements {@code e1} and {@code e2}
* in the list).
*
* <p>If the specified comparator is {@code null} then all elements in this
* list must implement the {@link Comparable} interface and the elements'
* {@linkplain Comparable natural ordering} should be used.
*
* <p>This list must be modifiable, but need not be resizable.
*
* @implSpec
* The default implementation obtains an array containing all elements in
* this list, sorts the array, and iterates over this list resetting each
* element from the corresponding position in the array. (This avoids the
* n<sup>2</sup> log(n) performance that would result from attempting
* to sort a linked list in place.)
*
* @implNote
* This implementation is a stable, adaptive, iterative mergesort that
* requires far fewer than n lg(n) comparisons when the input array is
* partially sorted, while offering the performance of a traditional
* mergesort when the input array is randomly ordered. If the input array
* is nearly sorted, the implementation requires approximately n
* comparisons. Temporary storage requirements vary from a small constant
* for nearly sorted input arrays to n/2 object references for randomly
* ordered input arrays.
*
* <p>The implementation takes equal advantage of ascending and
* descending order in its input array, and can take advantage of
* ascending and descending order in different parts of the same
* input array. It is well-suited to merging two or more sorted arrays:
* simply concatenate the arrays and sort the resulting array.
*
* <p>The implementation was adapted from Tim Peters's list sort for Python
* (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt">
* TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic
* Sorting and Information Theoretic Complexity", in Proceedings of the
* Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474,
* January 1993.
*
* @param c the {@code Comparator} used to compare list elements.
* A {@code null} value indicates that the elements'
* {@linkplain Comparable natural ordering} should be used
* @throws ClassCastException if the list contains elements that are not
* <i>mutually comparable</i> using the specified comparator
* @throws UnsupportedOperationException if the list's list-iterator does
* not support the {@code set} operation
* @throws IllegalArgumentException
* (<a href="Collection.html#optional-restrictions">optional</a>)
* if the comparator is found to violate the {@link Comparator}
* contract
* @since 1.8
*/
@SuppressWarnings({"unchecked", "rawtypes"})
default void sort(Comparator<? super E> c) {
Object[] a = this.toArray();
Arrays.sort(a, (Comparator) c);
ListIterator<E> i = this.listIterator();
for (Object e : a) {
i.next();
i.set((E) e);
}
}
/**
* Removes all of the elements from this list (optional operation).
* The list will be empty after this call returns.
*
* @throws UnsupportedOperationException if the {@code clear} operation
* is not supported by this list
*/
void clear();
// Comparison and hashing
/**
* Compares the specified object with this list for equality. Returns
* {@code true} if and only if the specified object is also a list, both
* lists have the same size, and all corresponding pairs of elements in
* the two lists are <i>equal</i>. (Two elements {@code e1} and
* {@code e2} are <i>equal</i> if {@code Objects.equals(e1, e2)}.)
* In other words, two lists are defined to be
* equal if they contain the same elements in the same order. This
* definition ensures that the equals method works properly across
* different implementations of the {@code List} interface.
*
* @param o the object to be compared for equality with this list
* @return {@code true} if the specified object is equal to this list
*/
boolean equals(Object o);
/**
* Returns the hash code value for this list. The hash code of a list
* is defined to be the result of the following calculation:
* <pre>{@code
* int hashCode = 1;
* for (E e : list)
* hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
* }</pre>
* This ensures that {@code list1.equals(list2)} implies that
* {@code list1.hashCode()==list2.hashCode()} for any two lists,
* {@code list1} and {@code list2}, as required by the general
* contract of {@link Object#hashCode}.
*
* @return the hash code value for this list
* @see Object#equals(Object)
* @see #equals(Object)
*/
int hashCode();
// Positional Access Operations
/**
* Returns the element at the specified position in this list.
*
* @param index index of the element to return
* @return the element at the specified position in this list
* @throws IndexOutOfBoundsException if the index is out of range
* ({@code index < 0 || index >= size()})
*/
E get(int index);
/**
* Replaces the element at the specified position in this list with the
* specified element (optional operation).
*
* @param index index of the element to replace
* @param element element to be stored at the specified position
* @return the element previously at the specified position
* @throws UnsupportedOperationException if the {@code set} operation
* is not supported by this list
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this list
* @throws NullPointerException if the specified element is null and
* this list does not permit null elements
* @throws IllegalArgumentException if some property of the specified
* element prevents it from being added to this list
* @throws IndexOutOfBoundsException if the index is out of range
* ({@code index < 0 || index >= size()})
*/
E set(int index, E element);
/**
* Inserts the specified element at the specified position in this list
* (optional operation). Shifts the element currently at that position
* (if any) and any subsequent elements to the right (adds one to their
* indices).
*
* @param index index at which the specified element is to be inserted
* @param element element to be inserted
* @throws UnsupportedOperationException if the {@code add} operation
* is not supported by this list
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this list
* @throws NullPointerException if the specified element is null and
* this list does not permit null elements
* @throws IllegalArgumentException if some property of the specified
* element prevents it from being added to this list
* @throws IndexOutOfBoundsException if the index is out of range
* ({@code index < 0 || index > size()})
*/
void add(int index, E element);
/**
* Removes the element at the specified position in this list (optional
* operation). Shifts any subsequent elements to the left (subtracts one
* from their indices). Returns the element that was removed from the
* list.
*
* @param index the index of the element to be removed
* @return the element previously at the specified position
* @throws UnsupportedOperationException if the {@code remove} operation
* is not supported by this list
* @throws IndexOutOfBoundsException if the index is out of range
* ({@code index < 0 || index >= size()})
*/
E remove(int index);
// Search Operations
/**
* Returns the index of the first occurrence of the specified element
* in this list, or -1 if this list does not contain the element.
* More formally, returns the lowest index {@code i} such that
* {@code Objects.equals(o, get(i))},
* or -1 if there is no such index.
*
* @param o element to search for
* @return the index of the first occurrence of the specified element in
* this list, or -1 if this list does not contain the element
* @throws ClassCastException if the type of the specified element
* is incompatible with this list
* (<a href="Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified element is null and this
* list does not permit null elements
* (<a href="Collection.html#optional-restrictions">optional</a>)
*/
int indexOf(Object o);
/**
* Returns the index of the last occurrence of the specified element
* in this list, or -1 if this list does not contain the element.
* More formally, returns the highest index {@code i} such that
* {@code Objects.equals(o, get(i))},
* or -1 if there is no such index.
*
* @param o element to search for
* @return the index of the last occurrence of the specified element in
* this list, or -1 if this list does not contain the element
* @throws ClassCastException if the type of the specified element
* is incompatible with this list
* (<a href="Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified element is null and this
* list does not permit null elements
* (<a href="Collection.html#optional-restrictions">optional</a>)
*/
int lastIndexOf(Object o);
// List Iterators
/**
* Returns a list iterator over the elements in this list (in proper
* sequence).
*
* @return a list iterator over the elements in this list (in proper
* sequence)
*/
ListIterator<E> listIterator();
/**
* Returns a list iterator over the elements in this list (in proper
* sequence), starting at the specified position in the list.
* The specified index indicates the first element that would be
* returned by an initial call to {@link ListIterator#next next}.
* An initial call to {@link ListIterator#previous previous} would
* return the element with the specified index minus one.
*
* @param index index of the first element to be returned from the
* list iterator (by a call to {@link ListIterator#next next})
* @return a list iterator over the elements in this list (in proper
* sequence), starting at the specified position in the list
* @throws IndexOutOfBoundsException if the index is out of range
* ({@code index < 0 || index > size()})
*/
ListIterator<E> listIterator(int index);
// View
/**
* Returns a view of the portion of this list between the specified
* {@code fromIndex}, inclusive, and {@code toIndex}, exclusive. (If
* {@code fromIndex} and {@code toIndex} are equal, the returned list is
* empty.) The returned list is backed by this list, so non-structural
* changes in the returned list are reflected in this list, and vice-versa.
* The returned list supports all of the optional list operations supported
* by this list.<p>
*
* This method eliminates the need for explicit range operations (of
* the sort that commonly exist for arrays). Any operation that expects
* a list can be used as a range operation by passing a subList view
* instead of a whole list. For example, the following idiom
* removes a range of elements from a list:
* <pre>{@code
* list.subList(from, to).clear();
* }</pre>
* Similar idioms may be constructed for {@code indexOf} and
* {@code lastIndexOf}, and all of the algorithms in the
* {@code Collections} class can be applied to a subList.<p>
*
* The semantics of the list returned by this method become undefined if
* the backing list (i.e., this list) is <i>structurally modified</i> in
* any way other than via the returned list. (Structural modifications are
* those that change the size of this list, or otherwise perturb it in such
* a fashion that iterations in progress may yield incorrect results.)
*
* @param fromIndex low endpoint (inclusive) of the subList
* @param toIndex high endpoint (exclusive) of the subList
* @return a view of the specified range within this list
* @throws IndexOutOfBoundsException for an illegal endpoint index value
* ({@code fromIndex < 0 || toIndex > size ||
* fromIndex > toIndex})
*/
List<E> subList(int fromIndex, int toIndex);
/**
* Creates a {@link Spliterator} over the elements in this list.
*
* <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and
* {@link Spliterator#ORDERED}. Implementations should document the
* reporting of additional characteristic values.
*
* @implSpec
* The default implementation creates a
* <em><a href="Spliterator.html#binding">late-binding</a></em>
* spliterator as follows:
* <ul>
* <li>If the list is an instance of {@link RandomAccess} then the default
* implementation creates a spliterator that traverses elements by
* invoking the method {@link List#get}. If such invocation results or
* would result in an {@code IndexOutOfBoundsException} then the
* spliterator will <em>fail-fast</em> and throw a
* {@code ConcurrentModificationException}.
* If the list is also an instance of {@link AbstractList} then the
* spliterator will use the list's {@link AbstractList#modCount modCount}
* field to provide additional <em>fail-fast</em> behavior.
* <li>Otherwise, the default implementation creates a spliterator from the
* list's {@code Iterator}. The spliterator inherits the
* <em>fail-fast</em> of the list's iterator.
* </ul>
*
* @implNote
* The created {@code Spliterator} additionally reports
* {@link Spliterator#SUBSIZED}.
*
* @return a {@code Spliterator} over the elements in this list
* @since 1.8
*/
@Override
default Spliterator<E> spliterator() {
if (this instanceof RandomAccess) {
return new AbstractList.RandomAccessSpliterator<>(this);
} else {
return Spliterators.spliterator(this, Spliterator.ORDERED);
}
}
/**
* Returns an unmodifiable list containing zero elements.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @return an empty {@code List}
*
* @since 9
*/
static <E> List<E> of() {
return ImmutableCollections.List0.instance();
}
/**
* Returns an unmodifiable list containing one element.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @param e1 the single element
* @return a {@code List} containing the specified element
* @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.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @param e1 the first element
* @param e2 the second element
* @return a {@code List} containing the specified elements
* @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.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
* @return a {@code List} containing the specified elements
* @throws NullPointerException if an element is {@code null}
*
* @since 9
*/
static <E> List<E> of(E e1, E e2, E e3) {
return new ImmutableCollections.ListN<>(e1, e2, e3);
}
/**
* Returns an unmodifiable list containing four elements.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
* @param e4 the fourth element
* @return a {@code List} containing the specified elements
* @throws NullPointerException if an element is {@code null}
*
* @since 9
*/
static <E> List<E> of(E e1, E e2, E e3, E e4) {
return new ImmutableCollections.ListN<>(e1, e2, e3, e4);
}
/**
* Returns an unmodifiable list containing five elements.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
* @param e4 the fourth element
* @param e5 the fifth element
* @return a {@code List} containing the specified elements
* @throws NullPointerException if an element is {@code null}
*
* @since 9
*/
static <E> List<E> of(E e1, E e2, E e3, E e4, E e5) {
return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5);
}
/**
* Returns an unmodifiable list containing six elements.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
* @param e4 the fourth element
* @param e5 the fifth element
* @param e6 the sixth element
* @return a {@code List} containing the specified elements
* @throws NullPointerException if an element is {@code null}
*
* @since 9
*/
static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6) {
return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
e6);
}
/**
* Returns an unmodifiable list containing seven elements.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
* @param e4 the fourth element
* @param e5 the fifth element
* @param e6 the sixth element
* @param e7 the seventh element
* @return a {@code List} containing the specified elements
* @throws NullPointerException if an element is {@code null}
*
* @since 9
*/
static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7) {
return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
e6, e7);
}
/**
* Returns an unmodifiable list containing eight elements.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
* @param e4 the fourth element
* @param e5 the fifth element
* @param e6 the sixth element
* @param e7 the seventh element
* @param e8 the eighth element
* @return a {@code List} containing the specified elements
* @throws NullPointerException if an element is {@code null}
*
* @since 9
*/
static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8) {
return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
e6, e7, e8);
}
/**
* Returns an unmodifiable list containing nine elements.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
* @param e4 the fourth element
* @param e5 the fifth element
* @param e6 the sixth element
* @param e7 the seventh element
* @param e8 the eighth element
* @param e9 the ninth element
* @return a {@code List} containing the specified elements
* @throws NullPointerException if an element is {@code null}
*
* @since 9
*/
static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9) {
return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
e6, e7, e8, e9);
}
/**
* Returns an unmodifiable list containing ten elements.
*
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @param <E> the {@code List}'s element type
* @param e1 the first element
* @param e2 the second element
* @param e3 the third element
* @param e4 the fourth element
* @param e5 the fifth element
* @param e6 the sixth element
* @param e7 the seventh element
* @param e8 the eighth element
* @param e9 the ninth element
* @param e10 the tenth element
* @return a {@code List} containing the specified elements
* @throws NullPointerException if an element is {@code null}
*
* @since 9
*/
static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9, E e10) {
return new ImmutableCollections.ListN<>(e1, e2, e3, e4, e5,
e6, e7, e8, e9, e10);
}
/**
* Returns an unmodifiable list containing an arbitrary number of elements.
* See <a href="#unmodifiable">Unmodifiable Lists</a> for details.
*
* @apiNote
* This method also accepts a single array as an argument. The element type of
* the resulting list will be the component type of the array, and the size of
* the list will be equal to the length of the array. To create a list with
* a single element that is an array, do the following:
*
* <pre>{@code
* String[] array = ... ;
* List<String[]> list = List.<String[]>of(array);
* }</pre>
*
* This will cause the {@link List#of(Object) List.of(E)} method
* to be invoked instead.
*
* @param <E> the {@code List}'s element type
* @param elements the elements to be contained in the list
* @return a {@code List} containing the specified elements
* @throws NullPointerException if an element is {@code null} or if the array is {@code null}
*
* @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,
* and it must not contain any null elements. If the given Collection is subsequently
* modified, the returned List will not reflect such modifications.
*
* @implNote
* If the given Collection is an <a href="#unmodifiable">unmodifiable List</a>,
* calling copyOf will generally not create a copy.
*
* @param <E> the {@code List}'s element type
* @param coll a {@code Collection} from which elements are drawn, must be non-null
* @return a {@code List} containing the elements of the given {@code Collection}
* @throws NullPointerException if coll is null, or if it contains any nulls
* @since 10
*/
@SuppressWarnings("unchecked")
static <E> List<E> copyOf(Collection<? extends E> coll) {
if (coll instanceof ImmutableCollections.AbstractImmutableList) {
return (List<E>)coll;
} else {
return (List<E>)List.of(coll.toArray());
}
}
}
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