Package android.util

Class SparseIntArray

  • All Implemented Interfaces:
    java.lang.Cloneable
    public class SparseIntArray
extends java.lang.Object
implements java.lang.Cloneable
    SparseIntArrays map integers to integers. Unlike a normal array of integers, there can be gaps in the indices. It is intended to be more memory efficient than using a HashMap to map Integers to Integers, both because it avoids auto-boxing keys and values 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%.

    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 will return the keys in ascending order, or the values corresponding to the keys in ascending order in the case of valueAt(int).

    • Constructor Summary

      Constructors 
      Constructor Description
      SparseIntArray()
      Creates a new SparseIntArray containing no mappings.
      SparseIntArray​(int initialCapacity)
      Creates a new SparseIntArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void append​(int key, int 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 SparseIntArray.
      SparseIntArray clone()  
      int[] copyKeys()
      Provides a copy of keys.
      void delete​(int key)
      Removes the mapping from the specified key, if there was any.
      int get​(int key)
      Gets the int mapped from the specified key, or 0 if no such mapping has been made.
      int get​(int key, int valueIfKeyNotFound)
      Gets the int mapped from the specified key, or the specified value 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​(int 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.
      int keyAt​(int index)
      Given an index in the range 0...size()-1, returns the key from the indexth key-value mapping that this SparseIntArray stores.
      void put​(int key, int 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 removeAt​(int index)
      Removes the mapping at the given index.
      void setValueAt​(int index, int value)
      Directly set the value at a particular index.
      int size()
      Returns the number of key-value mappings that this SparseIntArray currently stores.
      java.lang.String toString()
      int valueAt​(int index)
      Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this SparseIntArray stores.

      • Methods inherited from class java.lang.Object

        equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

    • Constructor Detail

      • SparseIntArray

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

      • SparseIntArray

        public SparseIntArray​(int initialCapacity)
        Creates a new SparseIntArray 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 Detail

      • clone

        public SparseIntArray clone()
        Overrides:
        clone in class java.lang.Object

      • get

        public int get​(int key)
        Gets the int mapped from the specified key, or 0 if no such mapping has been made.

      • get

        public int get​(int key,
               int valueIfKeyNotFound)
        Gets the int mapped from the specified key, or the specified value if no such mapping has been made.

      • delete

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

      • removeAt

        public void removeAt​(int index)
        Removes the mapping at the given index.

      • put

        public void put​(int key,
                int value)
        Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one.

      • size

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

      • 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 SparseIntArray 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.

      • valueAt

        public int valueAt​(int index)
        Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this SparseIntArray 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.

      • setValueAt

        public void setValueAt​(int index,
                       int value)
        Directly set the value at a particular index.

      • 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​(int 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. 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.

      • clear

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

      • append

        public void append​(int key,
                   int 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.

      • copyKeys

        public int[] copyKeys()
        Provides a copy of keys.

      • toString

        public java.lang.String toString()

        This implementation composes a string by iterating over its mappings.

        Overrides:
        toString in class java.lang.Object