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java.lang.Objectandroid.support.v4.util.LongSparseArray<E>
public class LongSparseArray<E>
SparseArray mapping longs to Objects, a version of the platform's
android.util.LongSparseArray
that can be used on older versions of the
platform. Unlike a normal array of Objects,
there can be gaps in the indices. It is intended to be more memory efficient
than using a HashMap to map Longs to Objects, both 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 traditional HashMap, since 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 not significant, 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 step of all removed entries. This garbage collection will need to be performed at any time the array needs to be grown or the the map size or entry values are retrieved.
Constructor Summary | |
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LongSparseArray()
Creates a new LongSparseArray containing no mappings. |
|
LongSparseArray(int initialCapacity)
Creates a new LongSparseArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings. |
Method Summary | |
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void |
append(long 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 LongSparseArray. |
LongSparseArray<E> |
clone()
|
void |
delete(long key)
Removes the mapping from the specified key, if there was any. |
E |
get(long key)
Gets the Object mapped from the specified key, or null
if no such mapping has been made. |
E |
get(long key,
E valueIfKeyNotFound)
Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made. |
int |
indexOfKey(long 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 key, or a negative number if no keys map to the
specified value. |
long |
keyAt(int index)
Given an index in the range 0...size()-1 , returns
the key from the index th key-value mapping that this
LongSparseArray stores. |
void |
put(long 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(long key)
Alias for delete(long) . |
void |
removeAt(int index)
Removes the mapping at the specified index. |
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
LongSparseArray stores. |
int |
size()
Returns the number of key-value mappings that this LongSparseArray currently stores. |
java.lang.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
LongSparseArray stores. |
Methods inherited from class java.lang.Object |
---|
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public LongSparseArray()
public LongSparseArray(int initialCapacity)
Method Detail |
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public LongSparseArray<E> clone()
clone
in class java.lang.Object
public E get(long key)
null
if no such mapping has been made.
public E get(long key, E valueIfKeyNotFound)
public void delete(long key)
public void remove(long key)
delete(long)
.
public void removeAt(int index)
public void put(long key, E value)
public int size()
public long keyAt(int index)
0...size()-1
, returns
the key from the index
th key-value mapping that this
LongSparseArray stores.
public E valueAt(int index)
0...size()-1
, returns
the value from the index
th key-value mapping that this
LongSparseArray stores.
public void setValueAt(int index, E value)
0...size()-1
, sets a new
value for the index
th key-value mapping that this
LongSparseArray stores.
public int indexOfKey(long key)
keyAt(int)
would return the
specified key, or a negative number if the specified
key is not mapped.
public int indexOfValue(E value)
valueAt(int)
would return the
specified key, 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.
public void clear()
public void append(long key, E value)
public java.lang.String toString()
This implementation composes a string by iterating over its mappings. If this map contains itself as a value, the string "(this Map)" will appear in its place.
toString
in class java.lang.Object
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