Tóm Tắt
ArrayList
public
class
ArrayList
extends AbstractList<E>
implements
List<E>,
RandomAccess,
Cloneable,
Serializable
Resizable-array implementation of the List interface. Implements
all optional list operations, and permits all elements, including
null. In addition to implementing the List interface,
this class provides methods to manipulate the size of the array that is
used internally to store the list. (This class is roughly equivalent to
Vector, except that it is unsynchronized.)
The size, isEmpty, get, set,
iterator, and listIterator operations run in constant
time. The add operation runs in amortized constant time,
that is, adding n elements requires O(n) time. All of the other operations
run in linear time (roughly speaking). The constant factor is low compared
to that for the LinkedList implementation.
Each ArrayList instance has a capacity. The capacity is
the size of the array used to store the elements in the list. It is always
at least as large as the list size. As elements are added to an ArrayList,
its capacity grows automatically. The details of the growth policy are not
specified beyond the fact that adding an element has constant amortized
time cost.
An application can increase the capacity of an ArrayList instance
before adding a large number of elements using the ensureCapacity
operation. This may reduce the amount of incremental reallocation.
Note that this implementation is not synchronized.
If multiple threads access an ArrayList instance concurrently,
and at least one of the threads modifies the list structurally, it
must be synchronized externally. (A structural modification is
any operation that adds or deletes one or more elements, or explicitly
resizes the backing array; merely setting the value of an element is not
a structural modification.) This is typically accomplished by
synchronizing on some object that naturally encapsulates the list.
If no such object exists, the list should be “wrapped” using the
Collections.synchronizedList
method. This is best done at creation time, to prevent accidental
unsynchronized access to the list:
List list = Collections.synchronizedList(new ArrayList(...));
The iterators returned by this class’s iterator and
listIterator methods are fail-fast:
if the list is structurally modified at any time after the iterator is
created, in any way except through the iterator’s own
remove or
add methods, the iterator will throw a
ConcurrentModificationException. Thus, in the face of
concurrent modification, the iterator fails quickly and cleanly, rather
than risking arbitrary, non-deterministic behavior at an undetermined
time in the future.
Note that the fail-fast behavior of an iterator cannot be guaranteed
as it is, generally speaking, impossible to make any hard guarantees in the
presence of unsynchronized concurrent modification. Fail-fast iterators
throw ConcurrentModificationException on a best-effort basis.
Therefore, it would be wrong to write a program that depended on this
exception for its correctness: the fail-fast behavior of iterators
should be used only to detect bugs.
This class is a member of the
Java Collections Framework.
See also:
CollectionListLinkedListVector
Summary
Inherited fields
From class
protected
int
modCount
The number of times this list has been structurally modified.
Public constructors
ArrayList(int initialCapacity)
Constructs an empty list with the specified initial capacity.
ArrayList()
Constructs an empty list with an initial capacity of ten.
ArrayList(Collection<? extends E> c)
Constructs a list containing the elements of the specified
collection, in the order they are returned by the collection’s
iterator.
Public methods
boolean
add(E e)
Appends the specified element to the end of this list.
void
add(int index, E element)
Inserts the specified element at the specified position in this
list.
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.
boolean
addAll(int index, Collection<? extends E> c)
Inserts all of the elements in the specified collection into this
list, starting at the specified position.
void
clear()
Removes all of the elements from this list.
Object
clone()
Returns a shallow copy of this ArrayList instance.
boolean
contains(Object o)
Returns true if this list contains the specified element.
void
ensureCapacity(int minCapacity)
Increases the capacity of this ArrayList instance, if
necessary, to ensure that it can hold at least the number of elements
specified by the minimum capacity argument.
void
forEach(Consumer<? super E> action)
E
get(int index)
Returns the element at the specified position in 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(int index)
Returns a list iterator over the elements in this list (in proper
sequence), starting at the specified position in the list.
ListIterator<E>
listIterator()
Returns a list iterator over the elements in this list (in proper
sequence).
E
remove(int index)
Removes the element at the specified position in this list.
boolean
remove(Object o)
Removes the first occurrence of the specified element from this list,
if it is present.
boolean
removeAll(Collection<?> c)
Removes from this list all of its elements that are contained in the
specified collection.
boolean
removeIf(Predicate<? super E> filter)
Removes all of the elements of this collection that satisfy the given
predicate.
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.
E
set(int index, E element)
Replaces the element at the specified position in this list with
the specified element.
int
size()
Returns the number of elements in this list.
void
sort(Comparator<? super E> c)
Sorts this list according to the order induced by the specified
Comparator.
Spliterator<E>
spliterator()
Creates a late-binding
and fail-fast 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.
void
trimToSize()
Trims the capacity of this ArrayList instance to be the
list’s current size.
Protected methods
void
removeRange(int fromIndex, int toIndex)
Removes from this list all of the elements whose index is between
fromIndex, inclusive, and toIndex, exclusive.
Inherited methods
From class
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).
void
clear()
Removes all of the elements from this list (optional operation).
boolean
equals(Object o)
Compares the specified object with this list for equality.
abstract
E
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 of the first occurrence of the specified element
in this list, or -1 if this list does not contain the element.
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(int index)
Returns a list iterator over the elements in this list (in proper
sequence), starting at the specified position in the list.
ListIterator<E>
listIterator()
Returns a list iterator over the elements in this list (in proper
sequence).
E
remove(int index)
Removes the element at the specified position in this list (optional
operation).
void
removeRange(int fromIndex, int toIndex)
Removes from this list all of the elements whose index is between
fromIndex, inclusive, and toIndex, exclusive.
E
set(int index, E element)
Replaces the element at the specified position in this list with the
specified element (optional operation).
List<E>
subList(int fromIndex, int toIndex)
Returns a view of the portion of this list between the specified
fromIndex, inclusive, and toIndex, exclusive.
From class
boolean
add(E e)
Ensures that this collection contains the specified element (optional
operation).
boolean
addAll(Collection<? extends E> c)
Adds all of the elements in the specified collection to this collection
(optional operation).
void
clear()
Removes all of the elements from this collection (optional operation).
boolean
contains(Object o)
Returns true if this collection contains the specified element.
boolean
containsAll(Collection<?> c)
Returns true if this collection contains all of the elements
in the specified collection.
boolean
isEmpty()
Returns true if this collection contains no elements.
abstract
Iterator<E>
iterator()
Returns an iterator over the elements contained in this collection.
boolean
remove(Object o)
Removes a single instance of the specified element from this
collection, if it is present (optional operation).
boolean
removeAll(Collection<?> c)
Removes all of this collection’s elements that are also contained in the
specified collection (optional operation).
boolean
retainAll(Collection<?> c)
Retains only the elements in this collection that are contained in the
specified collection (optional operation).
abstract
int
size()
Returns the number of elements in this collection.
<T>
T[]
toArray(T[] a)
Returns an array containing all of the elements in this collection;
the runtime type of the returned array is that of the specified array.
Object[]
toArray()
Returns an array containing all of the elements in this collection.
String
toString()
Returns a string representation of this collection.
From class
Object
clone()
Creates and returns a copy of this object.
boolean
equals(Object obj)
Indicates whether some other object is “equal to” this one.
void
finalize()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
final
Class<?>
getClass()
Returns the runtime class of this Object.
int
hashCode()
Returns a hash code value for the object.
final
void
notify()
Wakes up a single thread that is waiting on this object’s
monitor.
final
void
notifyAll()
Wakes up all threads that are waiting on this object’s monitor.
String
toString()
Returns a string representation of the object.
final
void
wait(long timeout, int nanos)
Causes the current thread to wait until another thread invokes the
notify() method or the
notifyAll() method for this object, or
some other thread interrupts the current thread, or a certain
amount of real time has elapsed.
final
void
wait(long timeout)
Causes the current thread to wait until either another thread invokes the
notify() method or the
notifyAll() method for this object, or a
specified amount of time has elapsed.
final
void
wait()
Causes the current thread to wait until another thread invokes the
notify() method or the
notifyAll() method for this object.
From interface
abstract
boolean
add(E e)
Appends the specified element to the end of this list (optional
operation).
abstract
void
add(int index, E element)
Inserts the specified element at the specified position in this list
(optional operation).
abstract
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).
abstract
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).
abstract
void
clear()
Removes all of the elements from this list (optional operation).
abstract
boolean
contains(Object o)
Returns true if this list contains the specified element.
abstract
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.
abstract
boolean
equals(Object o)
Compares the specified object with this list for equality.
abstract
E
get(int index)
Returns the element at the specified position in this list.
abstract
int
hashCode()
Returns the hash code value for this list.
abstract
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.
abstract
boolean
isEmpty()
Returns true if this list contains no elements.
abstract
Iterator<E>
iterator()
Returns an iterator over the elements in this list in proper sequence.
abstract
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.
abstract
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.
abstract
ListIterator<E>
listIterator()
Returns a list iterator over the elements in this list (in proper
sequence).
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, 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)
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, E e8)
Returns an unmodifiable list containing eight elements.
static
<E>
List<E>
of()
Returns an unmodifiable list containing zero 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.
static
<E>
List<E>
of(E e1, E e2)
Returns an unmodifiable list containing two elements.
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, 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)
Returns an unmodifiable list containing four elements.
static
<E>
List<E>
of(E e1)
Returns an unmodifiable list containing one element.
abstract
E
remove(int index)
Removes the element at the specified position in this list (optional
operation).
abstract
boolean
remove(Object o)
Removes the first occurrence of the specified element from this list,
if it is present (optional operation).
abstract
boolean
removeAll(Collection<?> c)
Removes from this list all of its elements that are contained in the
specified 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.
abstract
boolean
retainAll(Collection<?> c)
Retains only the elements in this list that are contained in the
specified collection (optional operation).
abstract
E
set(int index, E element)
Replaces the element at the specified position in this list with the
specified element (optional operation).
abstract
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.
abstract
List<E>
subList(int fromIndex, int toIndex)
Returns a view of the portion of this list between the specified
fromIndex, inclusive, and toIndex, exclusive.
abstract
Object[]
toArray()
Returns an array containing all of the elements in this list in proper
sequence (from first to last element).
abstract
<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.
From interface
abstract
boolean
add(E e)
Ensures that this collection contains the specified element (optional
operation).
abstract
boolean
addAll(Collection<? extends E> c)
Adds all of the elements in the specified collection to this collection
(optional operation).
abstract
void
clear()
Removes all of the elements from this collection (optional operation).
abstract
boolean
contains(Object o)
Returns true if this collection contains the specified element.
abstract
boolean
containsAll(Collection<?> c)
Returns true if this collection contains all of the elements
in the specified collection.
abstract
boolean
equals(Object o)
Compares the specified object with this collection for equality.
abstract
int
hashCode()
Returns the hash code value for this collection.
abstract
boolean
isEmpty()
Returns true if this collection contains no elements.
abstract
Iterator<E>
iterator()
Returns an iterator over the elements in this collection.
default
Stream<E>
parallelStream()
Returns a possibly parallel Stream with this collection as its
source.
abstract
boolean
remove(Object o)
Removes a single instance of the specified element from this
collection, if it is present (optional operation).
abstract
boolean
removeAll(Collection<?> c)
Removes all of this collection’s elements that are also contained in the
specified collection (optional operation).
default
boolean
removeIf(Predicate<? super E> filter)
Removes all of the elements of this collection that satisfy the given
predicate.
abstract
boolean
retainAll(Collection<?> c)
Retains only the elements in this collection that are contained in the
specified collection (optional operation).
abstract
int
size()
Returns the number of elements in this collection.
default
Spliterator<E>
spliterator()
Creates a Spliterator over the elements in this collection.
default
Stream<E>
stream()
Returns a sequential Stream with this collection as its source.
abstract
<T>
T[]
toArray(T[] a)
Returns an array containing all of the elements in this collection;
the runtime type of the returned array is that of the specified array.
abstract
Object[]
toArray()
Returns an array containing all of the elements in this collection.
default
<T>
T[]
toArray(IntFunction<T[]> generator)
Returns an array containing all of the elements in this collection,
using the provided generator function to allocate the returned array.
From interface
default
void
forEach(Consumer<? super T> action)
Performs the given action for each element of the Iterable
until all elements have been processed or the action throws an
exception.
abstract
Iterator<E>
iterator()
Returns an iterator over elements of type T.
default
Spliterator<E>
spliterator()
Creates a Spliterator over the elements described by this
Iterable.
Public constructors
ArrayList
Added in API level 1
public ArrayList (int initialCapacity)
Constructs an empty list with the specified initial capacity.
Parameters
initialCapacity
int: the initial capacity of the list
Throws
IllegalArgumentException
if the specified initial capacity
is negative
ArrayList
Added in API level 1
public ArrayList ()
Constructs an empty list with an initial capacity of ten.
ArrayList
Added in API level 1
public ArrayList (Collection<? extends E> c)
Constructs a list containing the elements of the specified
collection, in the order they are returned by the collection’s
iterator.
Parameters
c
Collection: the collection whose elements are to be placed into this list
Throws
NullPointerException
if the specified collection is null
Public methods
add
Added in API level 1
public boolean add (E e)
Appends the specified element to the end of this list.
Parameters
e
E: element to be appended to this list
Returns
boolean
true (as specified by Collection#add)
add
Added in API level 1
public void add (int index,
E element)
Inserts the specified element at the specified position in this
list. Shifts the element currently at that position (if any) and
any subsequent elements to the right (adds one to their indices).
Parameters
index
int: index at which the specified element is to be inserted
element
E: element to be inserted
Throws
IndexOutOfBoundsException
addAll
Added in API level 1
public 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. 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 list, and this
list is nonempty.)
Parameters
c
Collection: collection containing elements to be added to this list
Returns
boolean
true if this list changed as a result of the call
Throws
NullPointerException
if the specified collection is null
addAll
Added in API level 1
public boolean addAll (int index,
Collection<? extends E> c)
Inserts all of the elements in the specified collection into this
list, starting at the specified position. 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 the list in the order that they are returned by the
specified collection’s iterator.
Parameters
index
int: index at which to insert the first element from the
specified collection
c
Collection: collection containing elements to be added to this list
Returns
boolean
true if this list changed as a result of the call
Throws
IndexOutOfBoundsException
NullPointerException
if the specified collection is null
clear
Added in API level 1
public void clear ()
Removes all of the elements from this list. The list will
be empty after this call returns.
clone
Added in API level 1
public Object clone ()
Returns a shallow copy of this ArrayList instance. (The
elements themselves are not copied.)
Returns
Object
a clone of this ArrayList instance
contains
Added in API level 1
public 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
(o==null ? e==null : o.equals(e)).
Parameters
o
Object: element whose presence in this list is to be tested
Returns
boolean
true if this list contains the specified element
ensureCapacity
Added in API level 1
public void ensureCapacity (int minCapacity)
Increases the capacity of this ArrayList instance, if
necessary, to ensure that it can hold at least the number of elements
specified by the minimum capacity argument.
Parameters
minCapacity
int: the desired minimum capacity
forEach
Added in API level 24
public void forEach (Consumer<? super E> action)
Parameters
action
Consumer
get
Added in API level 1
public E get (int index)
Returns the element at the specified position in this list.
Parameters
index
int: index of the element to return
Returns
E
the element at the specified position in this list
Throws
IndexOutOfBoundsException
indexOf
Added in API level 1
public 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
(o==null ? get(i)==null : o.equals(get(i))),
or -1 if there is no such index.
Parameters
o
Object: element to search for
Returns
int
the index of the first occurrence of the specified element in
this list, or -1 if this list does not contain the element
isEmpty
Added in API level 1
public boolean isEmpty ()
Returns true if this list contains no elements.
Returns
boolean
true if this list contains no elements
iterator
Added in API level 1
public Iterator<E> iterator ()
Returns an iterator over the elements in this list in proper sequence.
The returned iterator is fail-fast.
Returns
Iterator<E>
an iterator over the elements in this list in proper sequence
lastIndexOf
Added in API level 1
public 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
(o==null ? get(i)==null : o.equals(get(i))),
or -1 if there is no such index.
Parameters
o
Object: element to search for
Returns
int
the index of the last occurrence of the specified element in
this list, or -1 if this list does not contain the element
listIterator
Added in API level 1
public 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.
The returned list iterator is fail-fast.
Parameters
index
int: index of the first element to be returned from the
list iterator (by a call to next)
Returns
ListIterator<E>
a list iterator over the elements in this list (in proper
sequence), starting at the specified position in the list
Throws
IndexOutOfBoundsException
listIterator
Added in API level 1
public ListIterator<E> listIterator ()
Returns a list iterator over the elements in this list (in proper
sequence).
The returned list iterator is fail-fast.
Returns
ListIterator<E>
a list iterator over the elements in this list (in proper
sequence)
See also:
listIterator(int)
remove
Added in API level 1
public E remove (int index)
Removes the element at the specified position in this list.
Shifts any subsequent elements to the left (subtracts one from their
indices).
Parameters
index
int: the index of the element to be removed
Returns
E
the element that was removed from the list
Throws
IndexOutOfBoundsException
remove
Added in API level 1
public boolean remove (Object o)
Removes the first occurrence of the specified element from this list,
if it is present. If the 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). Returns true if this list
contained the specified element (or equivalently, if this list
changed as a result of the call).
Parameters
o
Object: element to be removed from this list, if present
Returns
boolean
true if this list contained the specified element
removeAll
Added in API level 1
public boolean removeAll (Collection<?> c)
Removes from this list all of its elements that are contained in the
specified collection.
Parameters
c
Collection: collection containing elements to be removed from this list
Returns
boolean
true if this list changed as a result of the call
Throws
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:
Collection.contains(Object)
removeIf
Added in API level 24
public boolean removeIf (Predicate<? super E> filter)
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.
Parameters
filter
Predicate: a predicate which returns true for elements to be
removed
Returns
boolean
true if any elements were removed
replaceAll
Added in API level 24
public 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.
Parameters
operator
UnaryOperator: the operator to apply to each element
retainAll
Added in API level 1
public boolean retainAll (Collection<?> c)
Retains only the elements in this list that are contained in the
specified collection. In other words, removes from this list all
of its elements that are not contained in the specified collection.
Parameters
c
Collection: collection containing elements to be retained in this list
Returns
boolean
true if this list changed as a result of the call
Throws
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:
Collection.contains(Object)
set
Added in API level 1
public E set (int index,
E element)
Replaces the element at the specified position in this list with
the specified element.
Parameters
index
int: index of the element to replace
element
E: element to be stored at the specified position
Returns
E
the element previously at the specified position
Throws
IndexOutOfBoundsException
size
Added in API level 1
public int size ()
Returns the number of elements in this list.
Returns
int
the number of elements in this list
sort
Added in API level 24
public void sort (Comparator<? super E> c)
Sorts this list according to the order induced by the specified
Comparator.
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.
For apps running on and targeting Android versions greater than
Nougat (API level > 25), Collections#sort(List)
delegates to this method. Such apps must not call
Collections#sort(List) from this method. Instead, prefer
not overriding this method at all. If you must override it, consider
this implementation:
@Override
public void sort(Comparator<? super E> c) {
Object[] elements = toArray();
Arrays.sort(elements, c);
ListIterator<E> iterator = (ListIterator<Object>) listIterator();
for (Object element : elements) {
iterator.next();
iterator.set((E) element);
}
}
Parameters
c
Comparator: the Comparator used to compare list elements.
A null value indicates that the elements’
natural ordering should be used
spliterator
Added in API level 24
public Spliterator<E> spliterator ()
Creates a late-binding
and fail-fast Spliterator over the elements in this
list.
The Spliterator reports Spliterator#SIZED,
Spliterator#SUBSIZED, and Spliterator#ORDERED.
Overriding implementations should document the reporting of additional
characteristic values.
Returns
Spliterator<E>
a Spliterator over the elements in this list
subList
Added in API level 1
public 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.
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(java.lang.Object) and
lastIndexOf(java.lang.Object), and all of the algorithms in the
Collections class can be applied to a subList.
Similar idioms may be constructed forand, and all of the algorithms in theclass 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
int: low endpoint (inclusive) of the subList
toIndex
int: high endpoint (exclusive) of the subList
Returns
List<E>
a view of the specified range within this list
Throws
IndexOutOfBoundsException
IllegalArgumentException
toArray
Added in API level 1
public 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). The caller is thus free to modify the returned array.
This method acts as bridge between array-based and collection-based
APIs.
Returns
Object[]
an array containing all of the elements in this list in
proper sequence
toArray
Added in API level 1
public 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 collection 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.)
Parameters
a
T: the array into which the elements of the 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
T[]
an array containing the elements of the 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
trimToSize
Added in API level 1
public void trimToSize ()
Trims the capacity of this ArrayList instance to be the
list’s current size. An application can use this operation to minimize
the storage of an ArrayList instance.
Protected methods
removeRange
Added in API level 1
protected void removeRange (int fromIndex,
int toIndex)
Removes from this list all of the elements whose index is between
fromIndex, inclusive, and toIndex, exclusive.
Shifts any succeeding elements to the left (reduces their index).
This call shortens the list by (toIndex - fromIndex) elements.
(If toIndex==fromIndex, this operation has no effect.)
Parameters
fromIndex
int: index of first element to be removed
toIndex
int: index after last element to be removed
Throws
IndexOutOfBoundsException
if fromIndex or
toIndex is out of range
(fromIndex < 0 ||)
fromIndex >= size() ||
toIndex > size() ||
toIndex < fromIndex
