Module java.base
Package java.util

Interface List<E>

Type Parameters:
E - the type of elements in this list
All Superinterfaces:
Collection<E>, Iterable<E>, SequencedCollection<E>
All Known Implementing Classes:
AbstractList, AbstractSequentialList, ArrayList, AttributeList, CopyOnWriteArrayList, LinkedList, RoleList, RoleUnresolvedList, Stack, Vector
public interface List<E> extends SequencedCollection<E>
An ordered collection, where the user 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.

Unlike sets, lists typically allow duplicate elements. More formally, lists typically allow pairs of elements e1 and e2 such that 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.

The List interface places additional stipulations, beyond those specified in the Collection interface, on the contracts of the iterator, add, remove, equals, and hashCode methods. Declarations for other inherited methods are also included here for convenience.

The 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 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.

The List interface provides a special iterator, called a ListIterator, that allows element insertion and replacement, and bidirectional access in addition to the normal operations that the Iterator interface provides. A method is provided to obtain a list iterator that starts at a specified position in the list.

The 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.

The List interface provides two methods to efficiently insert and remove multiple elements at an arbitrary point in the list.

Note: While it is permissible for lists to contain themselves as elements, extreme caution is advised: the equals and hashCode methods are no longer well defined on such a list.

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 NullPointerException or 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.

Unmodifiable Lists

The List.of and List.copyOf static factory methods provide a convenient way to create unmodifiable lists. The List instances created by these methods have the following characteristics:

  • They are unmodifiable. Elements cannot be added, removed, or replaced. Calling any mutator method on the List will always cause UnsupportedOperationException to be thrown. However, if the contained elements are themselves mutable, this may cause the List's contents to appear to change.
  • They disallow null elements. Attempts to create them with null elements result in NullPointerException.
  • They are serializable if all elements are serializable.
  • 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.
  • The lists and their subList views implement the RandomAccess interface.
  • They are value-based. Programmers should treat instances that are equal as interchangeable and should not use them for synchronization, or unpredictable behavior may occur. For example, in a future release, synchronization may fail. Callers should make no assumptions about the identity of the returned instances. Factories are free to create new instances or reuse existing ones.
  • They are serialized as specified on the Serialized Form page.

This interface is a member of the Java Collections Framework.

Since:
1.2
See Also:

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    add(int index, E element)
    Inserts the specified element at the specified position in this list (optional operation).
    boolean
    add(E e)
    Appends the specified element to the end of this list (optional operation).
    boolean
    addAll(int index, Collection<? extends E> c)
    Inserts all of the elements in the specified collection into this list at the specified position (optional operation).
    boolean
    addAll(Collection<? extends E> 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).
    default void
    addFirst(E e)
    Adds an element as the first element of this collection (optional operation).
    default void
    addLast(E e)
    Adds an element as the last element of this collection (optional operation).
    void
    clear()
    Removes all of the elements from this list (optional operation).
    boolean
    contains(Object o)
    Returns true if this list contains the specified element.
    boolean
    containsAll(Collection<?> c)
    Returns true if this list contains all of the elements of the specified collection.
    static <E> List<E>
    copyOf(Collection<? extends E> coll)
    Returns an unmodifiable List containing the elements of the given Collection, in its iteration order.
    boolean
    equals(Object o)
    Compares the specified object with this list for equality.
    E
    get(int index)
    Returns the element at the specified position in this list.
    default E
    getFirst()
    Gets the first element of this collection.
    default E
    getLast()
    Gets the last element of this collection.
    int
    hashCode()
    Returns the hash code value for this list.
    int
    indexOf(Object o)
    Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
    boolean
    isEmpty()
    Returns true if this list contains no elements.
    Iterator<E>
    iterator()
    Returns an iterator over the elements in this list in proper sequence.
    int
    lastIndexOf(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.
    ListIterator<E>
    listIterator()
    Returns a list iterator over the elements in this list (in proper sequence).
    ListIterator<E>
    listIterator(int index)
    Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list.
    static <E> List<E>
    of()
    Returns an unmodifiable list containing zero elements.
    static <E> List<E>
    of(E e1)
    Returns an unmodifiable list containing one element.
    static <E> List<E>
    of(E... elements)
    Returns an unmodifiable list containing an arbitrary number of elements.
    static <E> List<E>
    of(E e1, E e2)
    Returns an unmodifiable list containing two elements.
    static <E> List<E>
    of(E e1, E e2, E e3)
    Returns an unmodifiable list containing three elements.
    static <E> List<E>
    of(E e1, E e2, E e3, E e4)
    Returns an unmodifiable list containing four elements.
    static <E> List<E>
    of(E e1, E e2, E e3, E e4, E e5)
    Returns an unmodifiable list containing five elements.
    static <E> List<E>
    of(E e1, E e2, E e3, E e4, E e5, E e6)
    Returns an unmodifiable list containing six elements.
    static <E> List<E>
    of(E e1, E e2, E e3, E e4, E e5, E e6, E e7)
    Returns an unmodifiable list containing seven elements.
    static <E> List<E>
    of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8)
    Returns an unmodifiable list containing eight elements.
    static <E> List<E>
    of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9)
    Returns an unmodifiable list containing nine elements.
    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)
    Returns an unmodifiable list containing ten elements.
    E
    remove(int index)
    Removes the element at the specified position in this list (optional operation).
    boolean
    remove(Object o)
    Removes the first occurrence of the specified element from this list, if it is present (optional operation).
    boolean
    removeAll(Collection<?> c)
    Removes from this list all of its elements that are contained in the specified collection (optional operation).
    default E
    removeFirst()
    Removes and returns the first element of this collection (optional operation).
    default E
    removeLast()
    Removes and returns the last element of this collection (optional operation).
    default void
    replaceAll(UnaryOperator<E> operator)
    Replaces each element of this list with the result of applying the operator to that element.
    boolean
    retainAll(Collection<?> c)
    Retains only the elements in this list that are contained in the specified collection (optional operation).
    default List<E>
    reversed()
    Returns a reverse-ordered view of this collection.
    E
    set(int index, E element)
    Replaces the element at the specified position in this list with the specified element (optional operation).
    int
    size()
    Returns the number of elements in this list.
    default void
    sort(Comparator<? super E> c)
    Sorts this list according to the order induced by the specified Comparator.
    default Spliterator<E>
    spliterator()
    Creates a Spliterator over the elements in this list.
    List<E>
    subList(int fromIndex, int toIndex)
    Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive.
    Object[]
    toArray()
    Returns an array containing all of the elements in this list in proper sequence (from first to last element).
    <T> T[]
    toArray(T[] a)
    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.

    Methods declared in interface java.util.Collection

    parallelStream, removeIf, stream, toArray

    Methods declared in interface java.lang.Iterable

    forEach

  • Method Details

    • size

      int size()
      Returns the number of elements in this list. If this list contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.
      Specified by:
      size in interface Collection<E>
      Returns:
      the number of elements in this list

    • isEmpty

      boolean isEmpty()
      Returns true if this list contains no elements.
      Specified by:
      isEmpty in interface Collection<E>
      Returns:
      true if this list contains no elements

    • contains

      boolean contains(Object o)
      Returns true if this list contains the specified element. More formally, returns true if and only if this list contains at least one element e such that Objects.equals(o, e).
      Specified by:
      contains in interface Collection<E>
      Parameters:
      o - element whose presence in this list is to be tested
      Returns:
      true if this list contains the specified element
      Throws:
      ClassCastException - if the type of the specified element is incompatible with this list (optional)
      NullPointerException - if the specified element is null and this list does not permit null elements (optional)

    • iterator

      Iterator<E> iterator()
      Returns an iterator over the elements in this list in proper sequence.
      Specified by:
      iterator in interface Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Returns:
      an iterator over the elements in this list in proper sequence

    • toArray

      Object[] toArray()
      Returns an array containing all of the elements in this list in proper sequence (from first to last element).

      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.

      This method acts as bridge between array-based and collection-based APIs.

      Specified by:
      toArray in interface Collection<E>
      Returns:
      an array containing all of the elements in this list in proper sequence
      See Also:

    • toArray

      <T> T[] toArray(T[] a)
      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.

      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 null. (This is useful in determining the length of the list only if the caller knows that the list does not contain any null elements.)

      Like the 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.

      Suppose 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 String: 

      
     String[] y = x.toArray(new String[0]);
      Note that toArray(new Object[0]) is identical in function to toArray().
      Specified by:
      toArray in interface Collection<E>
      Type Parameters:
      T - the component type of the array to contain the collection
      Parameters:
      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.
      Returns:
      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
      NullPointerException - if the specified array is null

    • add

      boolean add(E e)
      Appends the specified element to the end of this list (optional operation).

      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.

      Specified by:
      add in interface Collection<E>
      Parameters:
      e - element to be appended to this list
      Returns:
      true (as specified by Collection.add(E))
      Throws:
      UnsupportedOperationException - if the add operation is not supported by this list
      ClassCastException - if the class of the specified element prevents it from being added to this list
      NullPointerException - if the specified element is null and this list does not permit null elements
      IllegalArgumentException - if some property of this element prevents it from being added to this list

    • remove

      boolean remove(Object o)
      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 i such that Objects.equals(o, get(i)) (if such an element exists). Returns true if this list contained the specified element (or equivalently, if this list changed as a result of the call).
      Specified by:
      remove in interface Collection<E>
      Parameters:
      o - element to be removed from this list, if present
      Returns:
      true if this list contained the specified element
      Throws:
      ClassCastException - if the type of the specified element is incompatible with this list (optional)
      NullPointerException - if the specified element is null and this list does not permit null elements (optional)
      UnsupportedOperationException - if the remove operation is not supported by this list

    • containsAll

      boolean containsAll(Collection<?> c)
      Returns true if this list contains all of the elements of the specified collection.
      Specified by:
      containsAll in interface Collection<E>
      Parameters:
      c - collection to be checked for containment in this list
      Returns:
      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 (optional)
      NullPointerException - if the specified collection contains one or more null elements and this list does not permit null elements (optional), or if the specified collection is null
      See Also:

    • addAll

      boolean addAll(Collection<? extends E> 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.)
      Specified by:
      addAll in interface Collection<E>
      Parameters:
      c - collection containing elements to be added to this list
      Returns:
      true if this list changed as a result of the call
      Throws:
      UnsupportedOperationException - if the addAll operation is not supported by this list
      ClassCastException - if the class of an element of the specified collection prevents it from being added to this list
      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
      IllegalArgumentException - if some property of an element of the specified collection prevents it from being added to this list
      See Also:

    • addAll

      boolean addAll(int index, 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.)
      Parameters:
      index - index at which to insert the first element from the specified collection
      c - collection containing elements to be added to this list
      Returns:
      true if this list changed as a result of the call
      Throws:
      UnsupportedOperationException - if the addAll operation is not supported by this list
      ClassCastException - if the class of an element of the specified collection prevents it from being added to this list
      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
      IllegalArgumentException - if some property of an element of the specified collection prevents it from being added to this list
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index > size())

    • removeAll

      boolean removeAll(Collection<?> c)
      Removes from this list all of its elements that are contained in the specified collection (optional operation).
      Specified by:
      removeAll in interface Collection<E>
      Parameters:
      c - collection containing elements to be removed from this list
      Returns:
      true if this list changed as a result of the call
      Throws:
      UnsupportedOperationException - if the removeAll operation is not supported by this list
      ClassCastException - if the class of an element of this list is incompatible with the specified collection (optional)
      NullPointerException - if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null
      See Also:

    • retainAll

      boolean retainAll(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.
      Specified by:
      retainAll in interface Collection<E>
      Parameters:
      c - collection containing elements to be retained in this list
      Returns:
      true if this list changed as a result of the call
      Throws:
      UnsupportedOperationException - if the retainAll operation is not supported by this list
      ClassCastException - if the class of an element of this list is incompatible with the specified collection (optional)
      NullPointerException - if this list contains a null element and the specified collection does not permit null elements (optional), or if the specified collection is null
      See Also:

    • replaceAll

      default void replaceAll(UnaryOperator<E> operator)
      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.
      Implementation Requirements:
      The default implementation is equivalent to, for this list: 
      
     final ListIterator<E> li = list.listIterator();
     while (li.hasNext()) {
         li.set(operator.apply(li.next()));
     }
      If the list's list-iterator does not support the set operation then an UnsupportedOperationException will be thrown when replacing the first element.
      Parameters:
      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
      NullPointerException - if the specified operator is null or if the operator result is a null value and this list does not permit null elements (optional)
      Since:
      1.8

    • sort

      default void sort(Comparator<? super E> c)
      Sorts this list according to the order induced by the specified Comparator. The sort is stable: this method must not reorder equal elements.

      All elements in this list must be mutually comparable using the specified comparator (that is, c.compare(e1, e2) must not throw a ClassCastException for any elements e1 and e2 in the list).

      If the specified comparator is null then all elements in this list must implement the Comparable interface and the elements' natural ordering should be used.

      This list must be modifiable, but need not be resizable.

      Implementation Requirements:
      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 n2 log(n) performance that would result from attempting to sort a linked list in place.)
      Implementation Note:
      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.

      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.

      The implementation was adapted from Tim Peters's list sort for Python ( TimSort). 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.

      Parameters:
      c - the Comparator used to compare list elements. A null value indicates that the elements' natural ordering should be used
      Throws:
      ClassCastException - if the list contains elements that are not mutually comparable using the specified comparator
      UnsupportedOperationException - if the list's list-iterator does not support the set operation
      IllegalArgumentException - (optional) if the comparator is found to violate the Comparator contract
      Since:
      1.8

    • clear

      void clear()
      Removes all of the elements from this list (optional operation). The list will be empty after this call returns.
      Specified by:
      clear in interface Collection<E>
      Throws:
      UnsupportedOperationException - if the clear operation is not supported by this list

    • equals

      boolean equals(Object o)
      Compares the specified object with this list for equality. Returns 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 equal. (Two elements e1 and e2 are equal if 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 List interface.
      Specified by:
      equals in interface Collection<E>
      Overrides:
      equals in class Object
      Parameters:
      o - the object to be compared for equality with this list
      Returns:
      true if the specified object is equal to this list
      See Also:

    • hashCode

      int hashCode()
      Returns the hash code value for this list. The hash code of a list is defined to be the result of the following calculation: 
      
     int hashCode = 1;
     for (E e : list)
         hashCode = 31*hashCode + (e==null ? 0 : e.hashCode());
      This ensures that list1.equals(list2) implies that list1.hashCode()==list2.hashCode() for any two lists, list1 and list2, as required by the general contract of Object.hashCode().
      Specified by:
      hashCode in interface Collection<E>
      Overrides:
      hashCode in class Object
      Returns:
      the hash code value for this list
      See Also:

    • get

      E get(int index)
      Returns the element at the specified position in this list.
      Parameters:
      index - index of the element to return
      Returns:
      the element at the specified position in this list
      Throws:
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

    • set

      E set(int index, E element)
      Replaces the element at the specified position in this list with the specified element (optional operation).
      Parameters:
      index - index of the element to replace
      element - element to be stored at the specified position
      Returns:
      the element previously at the specified position
      Throws:
      UnsupportedOperationException - if the set operation is not supported by this list
      ClassCastException - if the class of the specified element prevents it from being added to this list
      NullPointerException - if the specified element is null and this list does not permit null elements
      IllegalArgumentException - if some property of the specified element prevents it from being added to this list
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

    • add

      void add(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).
      Parameters:
      index - index at which the specified element is to be inserted
      element - element to be inserted
      Throws:
      UnsupportedOperationException - if the add operation is not supported by this list
      ClassCastException - if the class of the specified element prevents it from being added to this list
      NullPointerException - if the specified element is null and this list does not permit null elements
      IllegalArgumentException - if some property of the specified element prevents it from being added to this list
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index > size())

    • remove

      E remove(int index)
      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.
      Parameters:
      index - the index of the element to be removed
      Returns:
      the element previously at the specified position
      Throws:
      UnsupportedOperationException - if the remove operation is not supported by this list
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

    • indexOf

      int indexOf(Object o)
      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 i such that Objects.equals(o, get(i)), or -1 if there is no such index.
      Parameters:
      o - element to search for
      Returns:
      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 (optional)
      NullPointerException - if the specified element is null and this list does not permit null elements (optional)

    • lastIndexOf

      int lastIndexOf(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 i such that Objects.equals(o, get(i)), or -1 if there is no such index.
      Parameters:
      o - element to search for
      Returns:
      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 (optional)
      NullPointerException - if the specified element is null and this list does not permit null elements (optional)

    • listIterator

      ListIterator<E> listIterator()
      Returns a list iterator over the elements in this list (in proper sequence).
      Returns:
      a list iterator over the elements in this list (in proper sequence)

    • listIterator

      ListIterator<E> listIterator(int index)
      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 next. An initial call to previous would return the element with the specified index minus one.
      Parameters:
      index - index of the first element to be returned from the list iterator (by a call to next)
      Returns:
      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 (index < 0 || index > size())

    • subList

      List<E> subList(int fromIndex, int toIndex)
      Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive. (If fromIndex and 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.

      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: 

      
      list.subList(from, to).clear();
      Similar idioms may be constructed for indexOf and lastIndexOf, and all of the algorithms in the Collections class can be applied to a subList.

      The semantics of the list returned by this method become undefined if the backing list (i.e., this list) is structurally modified 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.)

      Parameters:
      fromIndex - low endpoint (inclusive) of the subList
      toIndex - high endpoint (exclusive) of the subList
      Returns:
      a view of the specified range within this list
      Throws:
      IndexOutOfBoundsException - for an illegal endpoint index value (fromIndex < 0 || toIndex > size || fromIndex > toIndex)

    • spliterator

      default Spliterator<E> spliterator()
      Creates a Spliterator over the elements in this list.

      The Spliterator reports Spliterator.SIZED and Spliterator.ORDERED. Implementations should document the reporting of additional characteristic values.

      Specified by:
      spliterator in interface Collection<E>
      Specified by:
      spliterator in interface Iterable<E>
      Implementation Requirements:
      The default implementation creates a late-binding spliterator as follows:
      • If the list is an instance of RandomAccess then the default implementation creates a spliterator that traverses elements by invoking the method get(int). If such invocation results or would result in an IndexOutOfBoundsException then the spliterator will fail-fast and throw a ConcurrentModificationException. If the list is also an instance of AbstractList then the spliterator will use the list's modCount field to provide additional fail-fast behavior.
      • Otherwise, the default implementation creates a spliterator from the list's Iterator. The spliterator inherits the fail-fast of the list's iterator.
      Implementation Note:
      The created Spliterator additionally reports Spliterator.SUBSIZED.
      Returns:
      a Spliterator over the elements in this list
      Since:
      1.8

    • addFirst

      default void addFirst(E e)
      Adds an element as the first element of this collection (optional operation). After this operation completes normally, the given element will be a member of this collection, and it will be the first element in encounter order.
      Specified by:
      addFirst in interface SequencedCollection<E>
      Implementation Requirements:
      The implementation in this interface calls add(0, e).
      Parameters:
      e - the element to be added
      Throws:
      NullPointerException - if the specified element is null and this collection does not permit null elements
      UnsupportedOperationException - if this collection implementation does not support this operation
      Since:
      21

    • addLast

      default void addLast(E e)
      Adds an element as the last element of this collection (optional operation). After this operation completes normally, the given element will be a member of this collection, and it will be the last element in encounter order.
      Specified by:
      addLast in interface SequencedCollection<E>
      Implementation Requirements:
      The implementation in this interface calls add(e).
      Parameters:
      e - the element to be added.
      Throws:
      NullPointerException - if the specified element is null and this collection does not permit null elements
      UnsupportedOperationException - if this collection implementation does not support this operation
      Since:
      21

    • getFirst

      default E getFirst()
      Gets the first element of this collection.
      Specified by:
      getFirst in interface SequencedCollection<E>
      Implementation Requirements:
      If this List is not empty, the implementation in this interface returns the result of calling get(0). Otherwise, it throws NoSuchElementException.
      Returns:
      the retrieved element
      Throws:
      NoSuchElementException - if this collection is empty
      Since:
      21

    • getLast

      default E getLast()
      Gets the last element of this collection.
      Specified by:
      getLast in interface SequencedCollection<E>
      Implementation Requirements:
      If this List is not empty, the implementation in this interface returns the result of calling get(size() - 1). Otherwise, it throws NoSuchElementException.
      Returns:
      the retrieved element
      Throws:
      NoSuchElementException - if this collection is empty
      Since:
      21

    • removeFirst

      default E removeFirst()
      Removes and returns the first element of this collection (optional operation).
      Specified by:
      removeFirst in interface SequencedCollection<E>
      Implementation Requirements:
      If this List is not empty, the implementation in this interface returns the result of calling remove(0). Otherwise, it throws NoSuchElementException.
      Returns:
      the removed element
      Throws:
      NoSuchElementException - if this collection is empty
      UnsupportedOperationException - if this collection implementation does not support this operation
      Since:
      21

    • removeLast

      default E removeLast()
      Removes and returns the last element of this collection (optional operation).
      Specified by:
      removeLast in interface SequencedCollection<E>
      Implementation Requirements:
      If this List is not empty, the implementation in this interface returns the result of calling remove(size() - 1). Otherwise, it throws NoSuchElementException.
      Returns:
      the removed element
      Throws:
      NoSuchElementException - if this collection is empty
      UnsupportedOperationException - if this collection implementation does not support this operation
      Since:
      21

    • reversed

      default List<E> reversed()
      Returns a reverse-ordered view of this collection. The encounter order of elements in the returned view is the inverse of the encounter order of elements in this collection. The reverse ordering affects all order-sensitive operations, including those on the view collections of the returned view. If the collection implementation permits modifications to this view, the modifications "write through" to the underlying collection. Changes to the underlying collection might or might not be visible in this reversed view, depending upon the implementation.
      Specified by:
      reversed in interface SequencedCollection<E>
      Implementation Requirements:
      The implementation in this interface returns a reverse-ordered List view. The reversed() method of the view returns a reference to this List. Other operations on the view are implemented via calls to public methods on this List. The exact relationship between calls on the view and calls on this List is unspecified. However, order-sensitive operations generally delegate to the appropriate method with the opposite orientation. For example, calling getFirst on the view results in a call to getLast on this List.
      Returns:
      a reverse-ordered view of this collection, as a List
      Since:
      21

    • of

      static <E> List<E> of()
      Returns an unmodifiable list containing zero elements. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Returns:
      an empty List
      Since:
      9

    • of

      static <E> List<E> of(E e1)
      Returns an unmodifiable list containing one element. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Parameters:
      e1 - the single element
      Returns:
      a List containing the specified element
      Throws:
      NullPointerException - if the element is null
      Since:
      9

    • of

      static <E> List<E> of(E e1, E e2)
      Returns an unmodifiable list containing two elements. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Parameters:
      e1 - the first element
      e2 - the second element
      Returns:
      a List containing the specified elements
      Throws:
      NullPointerException - if an element is null
      Since:
      9

    • of

      static <E> List<E> of(E e1, E e2, E e3)
      Returns an unmodifiable list containing three elements. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Parameters:
      e1 - the first element
      e2 - the second element
      e3 - the third element
      Returns:
      a List containing the specified elements
      Throws:
      NullPointerException - if an element is null
      Since:
      9

    • of

      static <E> List<E> of(E e1, E e2, E e3, E e4)
      Returns an unmodifiable list containing four elements. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Parameters:
      e1 - the first element
      e2 - the second element
      e3 - the third element
      e4 - the fourth element
      Returns:
      a List containing the specified elements
      Throws:
      NullPointerException - if an element is null
      Since:
      9

    • of

      static <E> List<E> of(E e1, E e2, E e3, E e4, E e5)
      Returns an unmodifiable list containing five elements. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Parameters:
      e1 - the first element
      e2 - the second element
      e3 - the third element
      e4 - the fourth element
      e5 - the fifth element
      Returns:
      a List containing the specified elements
      Throws:
      NullPointerException - if an element is null
      Since:
      9

    • of

      static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6)
      Returns an unmodifiable list containing six elements. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Parameters:
      e1 - the first element
      e2 - the second element
      e3 - the third element
      e4 - the fourth element
      e5 - the fifth element
      e6 - the sixth element
      Returns:
      a List containing the specified elements
      Throws:
      NullPointerException - if an element is null
      Since:
      9

    • of

      static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7)
      Returns an unmodifiable list containing seven elements. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Parameters:
      e1 - the first element
      e2 - the second element
      e3 - the third element
      e4 - the fourth element
      e5 - the fifth element
      e6 - the sixth element
      e7 - the seventh element
      Returns:
      a List containing the specified elements
      Throws:
      NullPointerException - if an element is null
      Since:
      9

    • of

      static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8)
      Returns an unmodifiable list containing eight elements. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Parameters:
      e1 - the first element
      e2 - the second element
      e3 - the third element
      e4 - the fourth element
      e5 - the fifth element
      e6 - the sixth element
      e7 - the seventh element
      e8 - the eighth element
      Returns:
      a List containing the specified elements
      Throws:
      NullPointerException - if an element is null
      Since:
      9

    • of

      static <E> List<E> of(E e1, E e2, E e3, E e4, E e5, E e6, E e7, E e8, E e9)
      Returns an unmodifiable list containing nine elements. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Parameters:
      e1 - the first element
      e2 - the second element
      e3 - the third element
      e4 - the fourth element
      e5 - the fifth element
      e6 - the sixth element
      e7 - the seventh element
      e8 - the eighth element
      e9 - the ninth element
      Returns:
      a List containing the specified elements
      Throws:
      NullPointerException - if an element is null
      Since:
      9

    • of

      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)
      Returns an unmodifiable list containing ten elements. See Unmodifiable Lists for details.
      Type Parameters:
      E - the List's element type
      Parameters:
      e1 - the first element
      e2 - the second element
      e3 - the third element
      e4 - the fourth element
      e5 - the fifth element
      e6 - the sixth element
      e7 - the seventh element
      e8 - the eighth element
      e9 - the ninth element
      e10 - the tenth element
      Returns:
      a List containing the specified elements
      Throws:
      NullPointerException - if an element is null
      Since:
      9

    • of

      @SafeVarargs static <E> List<E> of(E... elements)
      Returns an unmodifiable list containing an arbitrary number of elements. See Unmodifiable Lists for details.
      API Note:
      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: 
      
     String[] array = ... ;
     List<String[]> list = List.<String[]>of(array);
      This will cause the List.of(E) method to be invoked instead.
      Type Parameters:
      E - the List's element type
      Parameters:
      elements - the elements to be contained in the list
      Returns:
      a List containing the specified elements
      Throws:
      NullPointerException - if an element is null or if the array is null
      Since:
      9

    • copyOf

      static <E> List<E> copyOf(Collection<? extends E> coll)
      Returns an unmodifiable List 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.
      Implementation Note:
      If the given Collection is an unmodifiable List, calling copyOf will generally not create a copy.
      Type Parameters:
      E - the List's element type
      Parameters:
      coll - a Collection from which elements are drawn, must be non-null
      Returns:
      a List containing the elements of the given Collection
      Throws:
      NullPointerException - if coll is null, or if it contains any nulls
      Since:
      10