Package icyllis.modernui.util

Class SparseArray<E>

java.lang.Object
icyllis.modernui.util.SparseArray<E>
All Implemented Interfaces:
Cloneable
public 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.

Modified from Android.

  • Constructor Summary

    Constructors
    Constructor
    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.

  • Method Summary

    Modifier and Type
    Method
    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()
     
    boolean
    containsKey(int key)
    Returns true if the key exists in the array.
    boolean
    containsValue(E value)
    Returns true if the specified value is mapped from any key.
    void
    delete(int key)
    Removes the mapping from the specified key, if there was any.
    void
    deleteAt(int index)
    Removes the mapping at the specified index, if there was any.
    boolean
    equals(Object o)
     
    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 defaultValue)
    Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made.
    int
    hashCode()
     
    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.
    boolean
    isEmpty()
    Return true if size() is 0.
    int
    keyAt(int index)
    Given an index in the range 0...size()-1, returns the key from the indexth key-value mapping that this SparseArray stores.
    E
    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
    putAll(SparseArray<? extends E> other)
    Copies all the mappings from the other to this map.
    E
    putIfAbsent(int key, E value)
    Add a new value to the array map only if the key does not already have a value or it is mapped to null.
    E
    remove(int key)
    Removes the mapping from the specified key, if there was any, returning the old value.
    boolean
    remove(int key, Object value)
    Remove an existing key from the array map only if it is currently mapped to value.
    E
    removeAt(int index)
    Removes the mapping at the specified index, if there was any, returning the old value.
    void
    removeAtRange(int index, int size)
    Remove a range of mappings as a batch.
    E
    replace(int key, E value)
    Replace the mapping for key only if it is already mapped to a value.
    boolean
    replace(int key, E oldValue, E newValue)
    Replace the mapping for key only if it is already mapped to a value.
    void
    setValueAt(int index, E value)
    Given an index in the range 0...size()-1, sets a new value for the indexth 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 indexth key-value mapping that this SparseArray stores.

    Methods inherited from class java.lang.Object

    finalize, getClass, notify, notifyAll, wait, wait, wait

  • Constructor Details

    • SparseArray

      public SparseArray()
      Creates a new SparseArray containing no mappings.

    • SparseArray

      public 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. If you supply an initial capacity of 0, the sparse array will be initialized with a light-weight representation not requiring any additional array allocations.

  • Method Details

    • get

      public E get(int key)
      Gets the Object mapped from the specified key, or null if no such mapping has been made.

    • get

      public E get(int key, E defaultValue)
      Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made.

    • delete

      public void delete(int key)
      Removes the mapping from the specified key, if there was any.

    • remove

      public E remove(int key)
      Removes the mapping from the specified key, if there was any, returning the old value.

    • remove

      public boolean remove(int key, Object value)
      Remove an existing key from the array map only if it is currently mapped to value.
      Parameters:
      key - The key of the mapping to remove.
      value - The value expected to be mapped to the key.
      Returns:
      Returns true if the mapping was removed.

    • deleteAt

      public void deleteAt(int index)
      Removes the mapping at the specified index, if there was any.
      Throws:
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

    • removeAt

      public E removeAt(int index)
      Removes the mapping at the specified index, if there was any, returning the old value.
      Throws:
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

    • removeAtRange

      public void removeAtRange(int index, int size)
      Remove a range of mappings as a batch.
      Parameters:
      index - Index to begin at
      size - Number of mappings to remove

    • replace

      @Nullable public E replace(int key, E value)
      Replace the mapping for key only if it is already mapped to a value.
      Parameters:
      key - The key of the mapping to replace.
      value - The value to store for the given key.
      Returns:
      Returns the previous mapped value or null.

    • replace

      public boolean replace(int key, E oldValue, E newValue)
      Replace the mapping for key only if it is already mapped to a value.
      Parameters:
      key - The key of the mapping to replace.
      oldValue - The value expected to be mapped to the key.
      newValue - The value to store for the given key.
      Returns:
      Returns true if the value was replaced.

    • put

      @Nullable public E 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.
      Returns:
      Returns the previous mapped value or null.

    • putAll

      public void putAll(@Nonnull SparseArray<? extends E> other)
      Copies all the mappings from the other to this map. The effect of this call is equivalent to that of calling put(int, Object) on this map once for each mapping from key to value in other.

    • putIfAbsent

      @Nullable public E putIfAbsent(int key, E value)
      Add a new value to the array map only if the key does not already have a value or it is mapped to null.
      Parameters:
      key - The key under which to store the value.
      value - The value to store for the given key.
      Returns:
      Returns the value that was stored for the given key, or null if there was no such key.

    • size

      public int size()
      Returns the number of key-value mappings that this SparseArray currently stores.

    • isEmpty

      public boolean isEmpty()
      Return true if size() is 0.
      Returns:
      true if size() is 0.

    • keyAt

      public int keyAt(int index)
      Given an index in the range 0...size()-1, returns the key from the indexth 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.

      Throws:
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

    • valueAt

      public E valueAt(int index)
      Given an index in the range 0...size()-1, returns the value from the indexth 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.

      Throws:
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

    • setValueAt

      public void setValueAt(int index, E value)
      Given an index in the range 0...size()-1, sets a new value for the indexth key-value mapping that this SparseArray stores.
      Throws:
      IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())

    • indexOfKey

      public 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.

    • indexOfValue

      public 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.

      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.

    • indexOfValueByValue

      public 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.

      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.

    • containsKey

      public boolean containsKey(int key)
      Returns true if the key exists in the array. This is equivalent to indexOfKey(int) >= 0.
      Parameters:
      key - Potential key in the mapping
      Returns:
      true if the key is defined in the mapping

    • containsValue

      public boolean containsValue(E value)
      Returns true if the specified value is mapped from any key.

    • clear

      public void clear()
      Removes all key-value mappings from this SparseArray.

    • append

      public 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.

    • toString

      public 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.

      Overrides:
      toString in class Object

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • clone

      public SparseArray<E> clone()
      Overrides:
      clone in class Object