class SparseArray<E> extends Object implements Cloneable
SparseArray
maps integers to Objects and, unlike a normal array of Objects,
its indices can contain gaps. SparseArray
is intended to be more memory-efficient
than a
HashMap
, because it avoids
auto-boxing keys and its data structure doesn't rely on an extra entry object
for each mapping.
Note that this container keeps its mappings in an array data structure,
using a binary search to find keys. The implementation is not intended to be appropriate for
data structures
that may contain large numbers of items. It is generally slower than a
HashMap
because lookups require a binary search,
and adds and removes require inserting
and deleting entries in the array. For containers holding up to hundreds of items,
the performance difference is less than 50%.
To help with performance, the container includes an optimization when removing keys: instead of compacting its array immediately, it leaves the removed entry marked as deleted. The entry can then be re-used for the same key or compacted later in a single garbage collection of all removed entries. This garbage collection must be performed whenever the array needs to be grown, or when the map size or entry values are retrieved.
It is possible to iterate over the items in this container using
keyAt(int)
and valueAt(int)
. Iterating over the keys using
keyAt(int)
with ascending values of the index returns the
keys in ascending order. In the case of valueAt(int)
, the
values corresponding to the keys are returned in ascending order.
I2P - as of 0.9.48, changed to use chars for the index, max value 65535
Constructor and Description |
---|
SparseArray()
Creates a new SparseArray containing no mappings.
|
SparseArray(int initialCapacity)
Creates a new SparseArray containing no mappings that will not
require any additional memory allocation to store the specified
number of mappings.
|
Modifier and Type | Method and Description |
---|---|
void |
append(int key,
E value)
Puts a key/value pair into the array, optimizing for the case where
the key is greater than all existing keys in the array.
|
void |
clear()
Removes all key-value mappings from this SparseArray.
|
SparseArray<E> |
clone() |
void |
delete(int key)
Removes the mapping from the specified key, if there was any.
|
E |
get(int key)
Gets the Object mapped from the specified key, or
null
if no such mapping has been made. |
E |
get(int key,
E valueIfKeyNotFound)
Gets the Object mapped from the specified key, or the specified Object
if no such mapping has been made.
|
int |
indexOfKey(int key)
Returns the index for which
keyAt(int) would return the
specified key, or a negative number if the specified
key is not mapped. |
int |
indexOfValue(E value)
Returns an index for which
valueAt(int) would return the
specified value, or a negative number if no keys map to the
specified value. |
int |
indexOfValueByValue(E value)
Returns an index for which
valueAt(int) would return the
specified value, or a negative number if no keys map to the
specified value. |
int |
keyAt(int index)
Given an index in the range
0...size()-1 , returns
the key from the index th key-value mapping that this
SparseArray stores. |
void |
put(int key,
E value)
Adds a mapping from the specified key to the specified value,
replacing the previous mapping from the specified key if there
was one.
|
void |
remove(int key)
Alias for
delete(int) . |
void |
removeAt(int index)
Removes the mapping at the specified index.
|
void |
removeAtRange(int index,
int size)
Remove a range of mappings as a batch.
|
E |
removeReturnOld(int key)
Removes the mapping from the specified key, if there was any, returning the old value.
|
void |
setValueAt(int index,
E value)
Given an index in the range
0...size()-1 , sets a new
value for the index th key-value mapping that this
SparseArray stores. |
int |
size()
Returns the number of key-value mappings that this SparseArray
currently stores.
|
String |
toString() |
E |
valueAt(int index)
Given an index in the range
0...size()-1 , returns
the value from the index th key-value mapping that this
SparseArray stores. |
public SparseArray()
public SparseArray(int initialCapacity)
public SparseArray<E> clone()
public E get(int key)
null
if no such mapping has been made.public E get(int key, E valueIfKeyNotFound)
key
- 0 MIN, 65535 MAXpublic void delete(int key)
key
- 0 MIN, 65535 MAXpublic E removeReturnOld(int key)
key
- 0 MIN, 65535 MAXpublic void remove(int key)
delete(int)
.public void removeAt(int index)
For indices outside of the range 0...size()-1
,
a ArrayIndexOutOfBoundsException
is thrown.
public void removeAtRange(int index, int size)
index
- Index to begin atsize
- Number of mappings to remove
For indices outside of the range 0...size()-1
,
the behavior is undefined.
public void put(int key, E value)
key
- 0 MIN, 65535 MAXpublic int size()
public int keyAt(int index)
0...size()-1
, returns
the key from the index
th key-value mapping that this
SparseArray stores.
The keys corresponding to indices in ascending order are guaranteed to
be in ascending order, e.g., keyAt(0)
will return the
smallest key and keyAt(size()-1)
will return the largest
key.
For indices outside of the range 0...size()-1
,
a ArrayIndexOutOfBoundsException
is thrown.
public E valueAt(int index)
0...size()-1
, returns
the value from the index
th key-value mapping that this
SparseArray stores.
The values corresponding to indices in ascending order are guaranteed
to be associated with keys in ascending order, e.g.,
valueAt(0)
will return the value associated with the
smallest key and valueAt(size()-1)
will return the value
associated with the largest key.
For indices outside of the range 0...size()-1
,
a ArrayIndexOutOfBoundsException
is thrown.
public void setValueAt(int index, E value)
0...size()-1
, sets a new
value for the index
th key-value mapping that this
SparseArray stores.
For indices outside of the range 0...size()-1
,
a ArrayIndexOutOfBoundsException
is thrown.
public int indexOfKey(int key)
keyAt(int)
would return the
specified key, or a negative number if the specified
key is not mapped.key
- 0 MIN, 65535 MAXpublic int indexOfValue(E value)
valueAt(int)
would return the
specified value, or a negative number if no keys map to the
specified value.
Beware that this is a linear search, unlike lookups by key, and that multiple keys can map to the same value and this will find only one of them.
Note also that unlike most collections' indexOf
methods,
this method compares values using ==
rather than equals
.
public int indexOfValueByValue(E value)
valueAt(int)
would return the
specified value, or a negative number if no keys map to the
specified value.
Beware that this is a linear search, unlike lookups by key, and that multiple keys can map to the same value and this will find only one of them.
Note also that this method uses equals
unlike indexOfValue
.
public void clear()
public void append(int key, E value)
key
- 0 MIN, 65535 MAX