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Class com.sun.java.util.collections.AbstractList
java.lang.Object
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+----com.sun.java.util.collections.AbstractCollection
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+----com.sun.java.util.collections.AbstractList
- public abstract class AbstractList
- extends AbstractCollection
- implements List
This class provides a skeletal implementation of the List interface to
minimize the effort required to implement this interface backed by a
"random access" data store (such as an array). For sequential access
data (such as a linked list), AbstractSequentialList should be used in
preference to this Class.
To implement an unmodifiable List, the programmer needs only to extend
this class and provide implementations for the get(int index) and size()
methods.
To implement a modifiable List, the programmer must additionally override
the set(int index, Object element) method (which otherwise throws an
UnsupportedOperationException. If the List is variable-size the
programmer must additionally override the add(int index, Object element)
and remove(int index) methods.
The programmer should generally provide a void (no argument) and
Collection constructor, as per the recommendation in the Collection
interface specification.
Unlike the other abstract Collection implementations, the programmer does
not have to provide an Iterator implementation; the iterator and
listIterator are implemented by this class, on top the "random access"
methods: get(int index), set(int index, Object element),
set(int index, Object element), add(int index, Object element) and
remove(int index).
The documentation for each non-abstract methods in this class describes its
implementation in detail. Each of these methods may be overridden if the
Collection being implemented admits a more efficient implementation.
- See Also:
- Collection, List, AbstractSequentialList, AbstractCollection
-
modCount
- The number of times this List has been structurally modified.
-
AbstractList()
-
-
add(int, Object)
- Inserts the specified element at the specified position in this List
(optional operation).
-
add(Object)
- Appends the specified element to the end of this List (optional
operation).
-
addAll(int, Collection)
- Inserts all of the elements in in the specified Collection into this
List at the specified position (optional operation).
-
equals(Object)
- Compares the specified Object with this List for equality.
-
get(int)
- Returns the element at the specified position in this List.
-
hashCode()
- Returns the hash code value for this List.
-
indexOf(Object)
- Returns the index in this List of the first occurence of the specified
element, or -1 if the List does not contain this element.
-
iterator()
- Returns an Iterator over the elements in this List in proper sequence.
-
lastIndexOf(Object)
- Returns the index in this List of the last occurence of the specified
element, or -1 if the List does not contain this element.
-
listIterator()
- Returns an Iterator of the elements in this List (in proper sequence).
-
listIterator(int)
- Returns a ListIterator of the elements in this List (in proper
sequence), starting at the specified position in the List.
-
remove(int)
- Removes the element at the specified position in this List (optional
operation).
-
set(int, Object)
- Replaces the element at the specified position in this List with the
specified element (optional operation).
-
subList(int, int)
- Returns a view of the portion of this List between fromIndex,
inclusive, and toIndex, exclusive.
modCount
protected transient int modCount
- The number of times this List has been structurally modified.
Structural modifications are those that change the size of the
List, or otherwise perturb it in such a fashion that iterations in
progress may yield incorrect results.
This field is used by the the Iterator and ListIterator implementation
returned by the iterator and listIterator methods. If the value of this
field changes unexpectedly, the Iterator (or ListIterator) will
throw a ConcurrentModificationException in response to the
next, remove, previous, set or add operations. This provides
fail-fast behavior, rather than non-deterministic behavior
in the face of concurrent modification during iteration.
Use of this field by subclasses is optional. If a
subclass wishes to provide fail-fast Iterators (and ListIterators),
then it merely has to increment this field in its add(int, Object) and
remove(int) methods (and any other methods that it overrides that
result in structural modifications to the List). A single call to
add(int, Object) or remove(int) must add no more than one
to this field, or the Iterators (and ListIterators) will throw
bogus ConcurrentModificationExceptions. If an implementation
does not wish to provide fail-fast Iterators, this field may be
ignored.
AbstractList
public AbstractList()
add
public boolean add(Object o)
- Appends the specified element to the end of this List (optional
operation).
This implementation calls add(size(), o)
.
Note that this implementation will throw an
UnsupportedOperationException unless add(int, Object) is overridden.
- Parameters:
- o - element to be appended to this List.
- Returns:
- true (as per the general contract of Collection.add).
- Throws: UnsupportedOperationException
- add is not supported
by this Set.
- Throws: ClassCastException
- class of the specified element
prevents it from being added to this Set.
- Throws: IllegalArgumentException
- some aspect of this element prevents
it from being added to this Collection.
- Overrides:
- add in class AbstractCollection
get
public abstract Object get(int index)
- 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.
- Throws: IndexOutOfBoundsException
- index is out of range (index
< 0 || index >= size()).
set
public Object set(int index,
Object element)
- Replaces the element at the specified position in this List with the
specified element (optional operation).
This implementation always throws an UnsupportedOperationException.
- Parameters:
- index - index of element to replace.
- element - element to be stored at the specified position.
- Returns:
- the element previously at the specified position.
- Throws: UnsupportedOperationException
- set is not supported
by this List.
- Throws: ClassCastException
- class of the specified element
prevents it from being added to this List.
- Throws: IllegalArgumentException
- some aspect of the specified
element prevents it from being added to this List.
- Throws: IndexOutOfBoundsException
- index out of range
(index < 0 || index >= size()).
add
public void add(int index,
Object 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).
This implementation always throws an UnsupportedOperationException.
- Parameters:
- index - index at which the specified element is to be inserted.
- element - element to be inserted.
- Throws: UnsupportedOperationException
- add is not supported
by this List.
- Throws: ClassCastException
- class of the specified element
prevents it from being added to this List.
- Throws: IllegalArgumentException
- some aspect of the specified
element prevents it from being added to this List.
- Throws: IndexOutOfBoundsException
- index is out of range
(index < 0 || index > size()).
remove
public Object 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.
This implementation always throws an UnsupportedOperationException.
- Parameters:
- index - the index of the element to removed.
- Returns:
- the element previously at the specified position.
- Throws: UnsupportedOperationException
- remove is not supported
by this List.
- Throws: IndexOutOfBoundsException
- index out of range (index
< 0 || index >= size()).
indexOf
public int indexOf(Object o)
- Returns the index in this List of the first occurence of the specified
element, or -1 if the 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.
This implementation first gets a ListIterator (with listIterator()).
Then, it iterates over the List until the specified element is found
or the end of the List is reached.
- Parameters:
- o - element to search for.
- index - initial position to search for the specified element.
- Returns:
- the index in this List of the first occurence of the specified
element, or -1 if the List does not contain this element.
- Throws: IndexOutOfBoundsException
- index out of range
(index < 0 || index >= size()).
lastIndexOf
public int lastIndexOf(Object o)
- Returns the index in this List of the last occurence of the specified
element, or -1 if the 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.
This implementation first gets a ListIterator pointing to the
end of the List (with listIterator(size())). Then, it iterates
backwards over the list until the specified element is found, or the
beginning of the list is reached.
- Parameters:
- o - element to search for.
- index - initial position to search for the specified element.
- Returns:
- the index in this List of the last occurence of the specified
element, or -1 if the List does not contain this element.
- Throws: IndexOutOfBoundsException
- index out of range
(index < 0 || index >= size()).
addAll
public boolean addAll(int index,
Collection c)
- Inserts all of the elements in 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 the 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.)
This implementation gets an Iterator over the specified Collection and
iterates over it, inserting the elements obtained from the Iterator into
this List at the appropriate position, one at a time, using add(int,
Object). Many implementations will override this method for efficiency.
Note that this implementation will throw an
UnsupportedOperationException unless add(int, Object) is overridden.
- 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.
- Throws: UnsupportedOperationException
- addAll is not supported
by this List.
- Throws: ClassCastException
- class of one of elements of the specified
Collection prevents it from being added to this List.
- Throws: IllegalArgumentException
- some aspect of one of elements of
the specified Collection prevents it from being added to
this List.
- Throws: IndexOutOfBoundsException
- index out of range (index
< 0 || index > size()).
iterator
public Iterator iterator()
- Returns an Iterator over the elements in this List in proper sequence.
This implementation returns a straightforward implementation of the
Iterator interface, relying on the the backing List's size(),
get(int), and remove(int) methods.
Note that the Iterator returned by this method will throw an
UnsupportedOperationException in response to its remove
method unless the List's remove(int) method is overridden.
This implementation can be made to throw runtime exceptions in the
face of concurrent modification, as described in the specification for
the (protected) modCount field.
- Returns:
- an Iterator over the elements in this List in proper sequence.
- Overrides:
- iterator in class AbstractCollection
- See Also:
- modCount
listIterator
public ListIterator listIterator()
- Returns an Iterator of the elements in this List (in proper sequence).
This implementation returns
listIterator(0)
.
- Returns:
- an Iterator of the elements in this List (in proper sequence).
- See Also:
- listIterator
listIterator
public ListIterator listIterator(int index)
- Returns a ListIterator of 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 nextElement. An initial call to previousElement
would return the element with the specified index minus one.
This implementation returns a straightforward implementation of the
ListIterator interface that extends the implementation of the Iterator
interface returned by iterator(). The ListIterator implementation
relies on the the backing List's get(int), set(int, Object),
add(int, Object) and remove(int) methods.
Note that the ListIterator returned by this implementation will throw
an UnsupportedOperationException in response to its remove, set and
add methods unless the List's remove(int), set(int, Object),
and add(int, Object) methods are overridden (respectively).
This implementation can be made to throw runtime exceptions in the
face of concurrent modification, as described in the specification for
the (protected) modCount field.
- Parameters:
- index - index of first element to be returned from the
ListIterator (by a call to getNext).
- Returns:
- a ListIterator of the elements in this List (in proper
sequence), starting at the specified position in the List.
- Throws: IndexOutOfBoundsException
- index is out of range
(index < 0 || index > size()).
- See Also:
- modCount
subList
public List subList(int fromIndex,
int toIndex)
- Returns a view of the portion of this List between fromIndex,
inclusive, and toIndex, exclusive. The returned List is backed by this
List, so 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 operating on 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 the List, or otherwise perturb it in such
a fashion that iterations in progress may yield incorrect results.)
This implementation returns a List that subclasses AbstractList. The
subclass stores, in private fields, the offset of the subList within
the backing list, the size of the subList (which can change over its
lifetime), and the expected modCount value of the backing list.
The subclass's set(int, Object), get(int), add(int, Object) and
remove(int) methods all delegate to the corresponding methods on the
backing List, after bounds-checking the index and adjusting for the
offset. The listIerator(int) method returns a "wrapper object"
over a listIterator on the backing List, which is created with the
corresponding method on the backing List. The iterator method
merely returns listIterator(), and the size method merely returns the
subclass's size field.
All methods first check to see if the actual modCount of the backing
list is equal to its expected value, and throw a
ConcurrentModificationException if it is not.
- Parameters:
- fromIndex - low endpoint (inclusive) of the subList.
- toKey - high endpoint (exclusive) of the subList.
- Returns:
- a view of the specified range within this List.
- Throws: IndexOutOfBoundsException
- Illegal endpoint index value
(fromIndex < 0 || toIndex > size || fromIndex > toIndex).
equals
public 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 (e1==null ? e2==null : e1.equals(e2))
.)
In other words, two Lists are defined to be equal if they contain the
same elements in the same order.
This implementation first checks if the specified object is this
List. If so, it returns true; if not, it checks if the specified
object is a List. If not, it returns false; if so, it iterates over
both lists, comparing corresponding pairs of elements. If any
comparison returns false, this method returns false. If either
Iterator runs out of elements before before the other it returns false
(as the Lists are of unequal length); otherwise it returns true when
the iterations complete.
- Parameters:
- o - the Object to be compared for equality with this List.
- Returns:
- true if the specified Object is equal to this List.
- Overrides:
- equals in class Object
hashCode
public int hashCode()
- Returns the hash code value for this List.
This implementation uses exactly the code that is used to define
the List hash function in the documentation for List.hashCode.
- Returns:
- the hash code value for this List.
- Overrides:
- hashCode in class Object
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