程序包 org.beetl.core.util

类 SparseArray<E>

java.lang.Object
org.beetl.core.util.SparseArray<E>
所有已实现的接口:
Cloneable
public class SparseArray<E> extends Object implements Cloneable
SparseArray 的内部是通过两个数组对数据进行存储的， key 为 int 数组， value 为 Object 数组 - SparseArray 比 HashMap 更省内存， - 在某些条件下性能更好，它避免了对 key 的自动装箱（int 转为 Integer 类型） - 由于是整数key，所以添加删除可以使用二分查找 - ... 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.

  • 构造器概要

    构造器
    构造器
    说明
    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.

  • 方法概要

    修饰符和类型
    方法
    说明
    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 indexth 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)
     
    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.

    从类继承的方法 java.lang.Object

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

  • 构造器详细资料

    • 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.

  • 方法详细资料

    • clone

      public SparseArray<E> clone()
      覆盖:
      clone 在类中 Object

    • 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 valueIfKeyNotFound)
      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.

    • removeReturnOld

      public E removeReturnOld(int key)

    • remove

      public void remove(int key)
      Alias for delete(int).

    • removeAt

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

    • removeAtRange

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

      For indices outside of the range 0...size()-1, the behavior is undefined.

    • put

      public 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.

    • size

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

    • 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.

    • 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.

    • 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.

    • 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.

      覆盖:
      toString 在类中 Object