SparseArray (Javadocs [I2P+ 2.11.0+]

java.lang.Object
- net.i2p.router.crypto.ratchet.SparseArray<E>

Type Parameters:

E - type of objects stored in this sparse array

All Implemented Interfaces:

Cloneable
```
class SparseArray<E>
extends Object
implements Cloneable
```
Memory-efficient sparse array implementation for integer-to-object mappings using binary search lookup, optimized for collections with up to hundreds of items
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 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 keys using keyAt(int) with ascending values of index returns keys in ascending order. In the case of valueAt(int), values corresponding to keys are returned in ascending order.
I2P - as of 0.9.48, changed to use chars for the index, max value 65535
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 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 keys using keyAt(int) with ascending values of the index returns keys in ascending order. In the case of valueAt(int), 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 Summary

Constructors
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.

Method Summary

All Methods Instance Methods Concrete Methods
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.

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - 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 Detail
  - 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.
    
    Parameters:
    
    key - 0 MIN, 65535 MAX
  - clear
```
public void clear()
```
    Removes all key-value mappings from this SparseArray.
  - clone
```
public SparseArray<E> clone()
```
    Overrides:
    
    clone in class Object
  - delete
```
public void delete(int key)
```
    Removes the mapping from the specified key, if there was any.
    
    Parameters:
    
    key - 0 MIN, 65535 MAX
  - 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.
    
    Parameters:
    
    key - 0 MIN, 65535 MAX
  - 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.
    
    Parameters:
    
    key - 0 MIN, 65535 MAX
  - 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.
  - 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.
    
    For indices outside of the range 0...size()-1, a ArrayIndexOutOfBoundsException is thrown.
  - 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.
    
    Parameters:
    
    key - 0 MIN, 65535 MAX
  - remove
```
public void remove(int key)
```
    Alias for delete(int).
  - removeAt
```
public void removeAt(int index)
```
    Removes the mapping at the specified index.
    For indices outside of the range 0...size()-1, a ArrayIndexOutOfBoundsException is thrown.
  - 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
    For indices outside of the range 0...size()-1, the behavior is undefined.
  - removeReturnOld
```
public E removeReturnOld(int key)
```
    Removes the mapping from the specified key, if there was any, returning the old value.
    
    Parameters:
    
    key - 0 MIN, 65535 MAX
  - 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.
    For indices outside of the range 0...size()-1, a ArrayIndexOutOfBoundsException is thrown.
  - size
```
public int size()
```
    Returns the number of key-value mappings that this SparseArray currently stores.
  - 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
  - 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.
    
    For indices outside of the range 0...size()-1, a ArrayIndexOutOfBoundsException is thrown.

Class SparseArray<E>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

SparseArray

SparseArray

Method Detail

append

clear

clone

delete

get

get

indexOfKey

indexOfValue

indexOfValueByValue

keyAt

put

remove

removeAt

removeAtRange

removeReturnOld

setValueAt

size

toString

valueAt