Spec-Zone .ru
спецификации, руководства, описания, API
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Spec-Zone .ru
спецификации, руководства, описания, API
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JavaTM 2 Platform Standard Edition |
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An ordered collection (also known as a sequence). 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.
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 a such a list.
Collection,
Set,
ArrayList,
LinkedList,
Vector,
Arrays.asList(Object[]),
Collections.nCopies(int, Object),
Collections.EMPTY_LIST,
AbstractList,
AbstractSequentialList| Method Summary | |
void |
add(int index,
Object element)
Inserts the specified element at the specified position in this list (optional operation). |
boolean |
add(Object o)
Appends the specified element to the end of this list (optional operation). |
boolean |
addAll(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). |
boolean |
addAll(int index,
Collection c)
Inserts all of the elements in the specified collection into this list at the specified position (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. |
boolean |
equals(Object o)
Compares the specified object with this list for equality. |
Object |
get(int index)
Returns the element at the specified position in this list. |
int |
hashCode()
Returns the hash code value for this list. |
int |
indexOf(Object o)
Returns the index in this list of the first occurrence of the specified element, or -1 if this list does not contain this element. |
boolean |
isEmpty()
Returns true if this list contains no elements. |
Iterator |
iterator()
Returns an iterator over the elements in this list in proper sequence. |
int |
lastIndexOf(Object o)
Returns the index in this list of the last occurrence of the specified element, or -1 if this list does not contain this element. |
ListIterator |
listIterator()
Returns a list iterator of the elements in this list (in proper sequence). |
ListIterator |
listIterator(int index)
Returns a list iterator of the elements in this list (in proper sequence), starting at the specified position in this list. |
Object |
remove(int index)
Removes the element at the specified position in this list (optional operation). |
boolean |
remove(Object o)
Removes the first occurrence in this list of the specified element (optional operation). |
boolean |
removeAll(Collection c)
Removes from this list all the elements that are contained in the specified collection (optional operation). |
boolean |
retainAll(Collection c)
Retains only the elements in this list that are contained in the specified collection (optional operation). |
Object |
set(int index,
Object 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. |
List |
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. |
Object[] |
toArray(Object[] a)
Returns an array containing all of the elements in this list in proper sequence; the runtime type of the returned array is that of the specified array. |
| Method Detail |
public int size()
public boolean isEmpty()
public boolean contains(Object o)
o - element whose presence in this list is to be tested.public Iterator iterator()
public Object[] toArray()
Arrays.asList(Object[])public Object[] toArray(Object[] a)
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.public boolean add(Object o)
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.
o - element to be appended to this list.public boolean remove(Object o)
o - element to be removed from this list, if present.public boolean containsAll(Collection c)
c - collection to be checked for containment in this list.contains(Object)public boolean addAll(Collection c)
c - collection whose elements are to be added to this list.add(Object)
public boolean addAll(int index,
Collection c)
index - index at which to insert first element from the specified
collection.c - elements to be inserted into this list.public boolean removeAll(Collection c)
c - collection that defines which elements will be removed from
this list.remove(Object),
contains(Object)public boolean retainAll(Collection c)
c - collection that defines which elements this set will retain.remove(Object),
contains(Object)public void clear()
public boolean equals(Object o)
o - the object to be compared for equality with this list.public int hashCode()
hashCode = 1;
Iterator i = list.iterator();
while (i.hasNext()) {
Object obj = i.next();
hashCode = 31*hashCode + (obj==null ? 0 : obj.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.Object.hashCode(),
Object.equals(Object),
equals(Object)public Object get(int index)
index - index of element to return.
public Object set(int index,
Object element)
index - index of element to replace.element - element to be stored at the specified position.
public void add(int index,
Object element)
index - index at which the specified element is to be inserted.element - element to be inserted.public Object remove(int index)
index - the index of the element to removed.public int indexOf(Object o)
o - element to search for.public int lastIndexOf(Object o)
o - element to search for.public ListIterator listIterator()
public ListIterator listIterator(int index)
index - index of first element to be returned from the
list iterator (by a call to the next method).
public List subList(int fromIndex,
int toIndex)
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 this 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.)
fromIndex - low endpoint (inclusive) of the subList.toKey - high endpoint (exclusive) of the subList.
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JavaTM 2 Platform Standard Edition |
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| PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
| SUMMARY: INNER | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD | |||||||||