java::util::List Class Reference

Inheritance diagram for java::util::List:

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java::util::AbstractListjava::util::Collectionjava::lang::Interfacejava::lang::Objectjava::util::AbstractSequentialListjava::util::ArrayListjava::util::LinkedList
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Collaboration diagram for java::util::List:

Collaboration graph
java::util::Collectionjava::lang::Interfacejava::lang::Object
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List of all members.


Detailed Description

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.

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.

Author:
Josh Bloch
Version:
1.36, 12/03/01
See also:
Collection

Set

ArrayList

LinkedList

Vector

Arrays::asList(Object[])

Collections::nCopies(int, Object)

Collections::EMPTY_LIST

AbstractList

AbstractSequentialList

Since:
1.2

Public Member Functions

virtual jboolean add (const ObjectRef &o)=0
 Appends the specified element to the end of this list (optional operation).
virtual void add (jint index, const ObjectRef &element)=0
 Inserts the specified element at the specified position in this list (optional operation).
virtual jboolean remove (const ObjectRef &o)=0
 Removes the first occurrence in this list of the specified element (optional operation).
virtual ObjectRef remove (jint index)=0
 Removes the element at the specified position in this list (optional operation).
virtual jboolean addAll (const Collection &c)=0
 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).
virtual jboolean addAll (jint index, const Collection &c)=0
 Inserts all of the elements in the specified collection into this list at the specified position (optional operation).
virtual ObjectRef get (jint index) const =0
 Returns the element at the specified position in this list.
virtual ObjectRef set (jint index, const ObjectRef &element)=0
 Replaces the element at the specified position in this list with the specified element (optional operation).
virtual jint indexOf (const ObjectRef &o) const =0
 Returns the index in this list of the first occurrence of the specified element, or -1 if this list does not contain this element.
virtual jint lastIndexOf (const ObjectRef &o) const =0
 Returns the index in this list of the last occurrence of the specified element, or -1 if this list does not contain this element.
virtual Ref
< ListIterator
listIterator (jint index=0) const =0
 Returns a list iterator of the elements in this list (in proper sequence), starting at the specified position in this list.
virtual Ref< ListsubList (jint fromIndex, jint toIndex) const =0
 Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive.

Static Public Member Functions

static Ref< ListemptyList ()
 The empty list (immutable).
static Ref< ListsingletonList (const ObjectRef &o)
 Returns an immutable list containing only the specified object.
static Ref< ListsynchronizedList (const Ref< List > &c, const Ref< Sync > &sync=0)
 Returns a synchronized (thread-safe) list backed by the specified list.
static Ref< ListimmutableList (const Ref< List > &c)
 Returns an unmodifiable view of the specified list.

Member Function Documentation

static Ref<List> java::util::List::emptyList (  )  [static]

The empty list (immutable).

static Ref<List> java::util::List::singletonList ( const ObjectRef o  )  [static]

Returns an immutable list containing only the specified object.

Parameters:
o the sole object to be stored in the returned list.
Returns:
an immutable list containing only the specified object.
Since:
1.3

static Ref<List> java::util::List::synchronizedList ( const Ref< List > &  c,
const Ref< Sync > &  sync = 0 
) [static]

Returns a synchronized (thread-safe) list backed by the specified list.

In order to guarantee serial access, it is critical that all access to the backing list is accomplished through the returned list.

It is imperative that the user manually synchronize on the returned list when iterating over it:

  List list = Collections.synchronizedList(new ArrayList());
      ...
  synchronized(list) {
      Iterator i = list.iterator(); // Must be in synchronized block
      while (i.hasNext())
          foo(i.next());
  }
 
Failure to follow this advice may result in non-deterministic behavior.

The returned list will be serializable if the specified list is serializable.

Parameters:
list the list to be "wrapped" in a synchronized list.
Returns:
a synchronized view of the specified list.

static Ref<List> java::util::List::immutableList ( const Ref< List > &  c  )  [static]

Returns an unmodifiable view of the specified list.

This method allows modules to provide users with "read-only" access to internal lists. Query operations on the returned list "read through" to the specified list, and attempts to modify the returned list, whether direct or via its iterator, result in an UnsupportedOperationException.

The returned list will be serializable if the specified list is serializable. Similarly, the returned list will implement RandomAccess if the specified list does. the

Parameters:
list the list for which an unmodifiable view is to be returned.
Returns:
an unmodifiable view of the specified list.

virtual jboolean java::util::List::add ( const ObjectRef o  )  [pure virtual]

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.

Parameters:
o element to be appended to this list.
Returns:
true (as per the general contract of the Collection.add method).
Exceptions:
UnsupportedOperationException if the add method 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 support null elements.
IllegalArgumentException if some aspect of this element prevents it from being added to this list.

Implements java::util::Collection.

Implemented in java::util::AbstractList, java::util::ArrayList, and java::util::LinkedList.

virtual void java::util::List::add ( jint  index,
const ObjectRef element 
) [pure virtual]

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.
Exceptions:
UnsupportedOperationException if the add method 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 support null elements.
IllegalArgumentException if some aspect of the specified element prevents it from being added to this list.
IndexOutOfBoundsException if the index is out of range (index < 0 || index > size()).

Implemented in java::util::AbstractList, java::util::AbstractSequentialList, java::util::ArrayList, and java::util::LinkedList.

virtual jboolean java::util::List::remove ( const ObjectRef o  )  [pure virtual]

Removes the first occurrence in this list of the specified element (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 (o==null ? get(i)==null : o.equals(get(i))) (if such an element exists).

Parameters:
o element to be removed from this list, if present.
Returns:
true if this list contained the specified element.
Exceptions:
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 support null elements (optional).
UnsupportedOperationException if the remove method is not supported by this list.

Implements java::util::Collection.

Implemented in java::util::AbstractList, java::util::ArrayList, and java::util::LinkedList.

virtual ObjectRef java::util::List::remove ( jint  index  )  [pure virtual]

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 removed.
Returns:
the element previously at the specified position.
Exceptions:
UnsupportedOperationException if the remove method is not supported by this list.
IndexOutOfBoundsException if the index is out of range (index < 0 || index >= size()).

Implemented in java::util::AbstractList, java::util::AbstractSequentialList, java::util::ArrayList, and java::util::LinkedList.

virtual jboolean java::util::List::addAll ( const Collection c  )  [pure virtual]

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 unspecified 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:
c collection whose elements are to be added to this list.
Returns:
true if this list changed as a result of the call.
Exceptions:
UnsupportedOperationException if the addAll method is not supported by this list.
ClassCastException if the class of an element in 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 support null elements, or if the specified collection is null.
IllegalArgumentException if some aspect of an element in the specified collection prevents it from being added to this list.
See also:
add(Object)

Implements java::util::Collection.

Implemented in java::util::AbstractList, java::util::ArrayList, and java::util::LinkedList.

virtual jboolean java::util::List::addAll ( jint  index,
const Collection c 
) [pure virtual]

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 unspecified 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 first element from the specified collection.
c elements to be inserted into this list.
Returns:
true if this list changed as a result of the call.
Exceptions:
UnsupportedOperationException if the addAll method is not supported by this list.
ClassCastException if the class of one of elements 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 support null elements, or if the specified collection is null.
IllegalArgumentException if some aspect of one of elements of the specified collection prevents it from being added to this list.
IndexOutOfBoundsException if the index is out of range (index < 0 || index > size()).

Implemented in java::util::AbstractList, java::util::AbstractSequentialList, java::util::ArrayList, and java::util::LinkedList.

virtual ObjectRef java::util::List::get ( jint  index  )  const [pure virtual]

Returns the element at the specified position in this list.

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

Implemented in java::util::AbstractList, java::util::AbstractSequentialList, java::util::ArrayList, and java::util::LinkedList.

virtual ObjectRef java::util::List::set ( jint  index,
const ObjectRef element 
) [pure virtual]

Replaces the element at the specified position in this list with the specified element (optional operation).

Parameters:
index index of element to replace.
element element to be stored at the specified position.
Returns:
the element previously at the specified position.
Exceptions:
UnsupportedOperationException if the set method 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 support null elements.
IllegalArgumentException if some aspect of the specified element prevents it from being added to this list.
IndexOutOfBoundsException if the index is out of range (index < 0 || index >= size()).

Implemented in java::util::AbstractList, java::util::AbstractSequentialList, java::util::ArrayList, and java::util::LinkedList.

virtual jint java::util::List::indexOf ( const ObjectRef o  )  const [pure virtual]

Returns the index in this list of the first occurrence of the specified element, or -1 if this list does not contain this element.

More formally, returns the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.

Parameters:
o element to search for.
Returns:
the index in this list of the first occurrence of the specified element, or -1 if this list does not contain this element.
Exceptions:
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 support null elements (optional).

Implemented in java::util::AbstractList, java::util::ArrayList, and java::util::LinkedList.

virtual jint java::util::List::lastIndexOf ( const ObjectRef o  )  const [pure virtual]

Returns the index in this list of the last occurrence of the specified element, or -1 if this list does not contain this element.

More formally, returns the highest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.

Parameters:
o element to search for.
Returns:
the index in this list of the last occurrence of the specified element, or -1 if this list does not contain this element.
Exceptions:
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 support null elements (optional).

Implemented in java::util::AbstractList, java::util::ArrayList, and java::util::LinkedList.

virtual Ref<ListIterator> java::util::List::listIterator ( jint  index = 0  )  const [pure virtual]

Returns a list iterator of the elements in this list (in proper sequence), starting at the specified position in this list.

The specified index indicates the first element that would be returned by an initial call to the next method. An initial call to the previous method would return the element with the specified index minus one.

Parameters:
index index of first element to be returned from the list iterator (by a call to the next method).
Returns:
a list iterator of the elements in this list (in proper sequence), starting at the specified position in this list.
Exceptions:
IndexOutOfBoundsException if the index is out of range (index < 0 || index > size()).

Implemented in java::util::AbstractList, java::util::AbstractSequentialList, and java::util::LinkedList.

virtual Ref<List> java::util::List::subList ( jint  fromIndex,
jint  toIndex 
) const [pure virtual]

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.
Exceptions:
IndexOutOfBoundsException for an illegal endpoint index value (fromIndex < 0 || toIndex > size || fromIndex > toIndex).

Implemented in java::util::AbstractList.


The documentation for this class was generated from the following file:
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