| java.lang.Object | |
| ↳ | android.util.ArrayMap<K, V> |
ArrayMap is a generic key->value mapping data structure that is
designed to be more memory efficient than a traditional HashMap.
It keeps its mappings in an array data structure -- an integer array of hash
codes for each item, and an Object array of the key/value pairs. This allows it to
avoid having to create an extra object for every entry put in to the map, and it
also tries to control the growth of the size of these arrays more aggressively
(since growing them only requires copying the entries in the array, not rebuilding
a hash map).
Note that this 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%.
Because this container is intended to better balance memory use, unlike most other standard Java containers it will shrink its array as items are removed from it. Currently you have no control over this shrinking -- if you set a capacity and then remove an item, it may reduce the capacity to better match the current size. In the future an explicit call to set the capacity should turn off this aggressive shrinking behavior.
| Public Constructors | |||||||||||
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Create a new empty ArrayMap.
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Create a new ArrayMap with a given initial capacity.
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Create a new ArrayMap with the mappings from the given ArrayMap.
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| Public Methods | |||||||||||
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Make the array map empty.
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Determine if the array map contains all of the keys in the given collection.
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Check whether a key exists in the array.
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Check whether a value exists in the array.
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Ensure the array map can hold at least minimumCapacity
items.
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Return a
Set for iterating over and interacting with all mappings
in the array map.
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Compares this instance with the specified object and indicates if they
are equal.
This implementation returns false if the object is not a map, or if the maps have different sizes. | |||||||||||
Retrieve a value from the array.
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Returns an integer hash code for this object.
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Returns the index of a key in the set.
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Return true if the array map contains no items.
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Return the key at the given index in the array.
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Return a
Set for iterating over and interacting with all keys
in the array map.
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Add a new value to the array map.
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Perform a
put(Object, Object) of all key/value pairs in array
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Perform a
put(Object, Object) of all key/value pairs in map
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Remove an existing key from the array map.
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Remove all keys in the array map that exist in the given collection.
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Remove the key/value mapping at the given index.
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Remove all keys in the array map that do not exist in the given collection.
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Set the value at a given index in the array.
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Return the number of items in this array map.
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Returns a string containing a concise, human-readable description of this
object.
This implementation composes a string by iterating over its mappings. | |||||||||||
Return the value at the given index in the array.
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Return a
Collection for iterating over and interacting with all values
in the array map.
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[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.Object
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From interface
java.util.Map
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Create a new empty ArrayMap. The default capacity of an array map is 0, and will grow once items are added to it.
Create a new ArrayMap with a given initial capacity.
Create a new ArrayMap with the mappings from the given ArrayMap.
Determine if the array map contains all of the keys in the given collection.
| collection | The collection whose contents are to be checked against. |
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Check whether a key exists in the array.
| key | The key to search for. |
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Check whether a value exists in the array. This requires a linear search through the entire array.
| value | The value to search for. |
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Ensure the array map can hold at least minimumCapacity items.
Return a Set for iterating over and interacting with all mappings
in the array map.
Note: this is a very inefficient way to access the array contents, it requires generating a number of temporary objects and allocates additional state information associated with the container that will remain for the life of the container.
Note:
the semantics of this Set are subtly different than that of a
Developers
HashMap: most important,
the Map.Entry object returned by its iterator is a single
object that exists for the entire iterator, so you can not hold on to it
after calling Iterator.next.
Compares this instance with the specified object and indicates if they
are equal. In order to be equal, o must represent the same object
as this instance using a class-specific comparison. The general contract
is that this comparison should be reflexive, symmetric, and transitive.
Also, no object reference other than null is equal to null.
The default implementation returns true only if this ==
o. See Writing a correct
equals method
if you intend implementing your own equals method.
The general contract for the equals and hashCode() methods is that if equals returns true for
any two objects, then hashCode() must return the same value for
these objects. This means that subclasses of Object usually
override either both methods or neither of them.
This implementation returns false if the object is not a map, or if the maps have different sizes. Otherwise, for each key in this map, values of both maps are compared. If the values for any key are not equal, the method returns false, otherwise it returns true.
| object | the object to compare this instance with. |
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true if the specified object is equal to this Object; false otherwise.Retrieve a value from the array.
| key | The key of the value to retrieve. |
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Returns an integer hash code for this object. By contract, any two
objects for which equals(Object) returns true must return
the same hash code value. This means that subclasses of Object
usually override both methods or neither method.
Note that hash values must not change over time unless information used in equals comparisons also changes.
See Writing a correct
hashCode method
if you intend implementing your own hashCode method.
Returns the index of a key in the set.
| key | The key to search for. |
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Return true if the array map contains no items.
true if this map has no elements, false
otherwise.Return the key at the given index in the array.
| index | The desired index, must be between 0 and size()-1. |
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Return a Set for iterating over and interacting with all keys
in the array map.
Note: this is a fairly inefficient way to access the array contents, it requires generating a number of temporary objects and allocates additional state information associated with the container that will remain for the life of the container.
Add a new value to the array map.
| key | The key under which to store the value. If this key already exists in the array, its value will be replaced. |
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| value | The value to store for the given key. |
Perform a put(Object, Object) of all key/value pairs in array
| array | The array whose contents are to be retrieved. |
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Perform a put(Object, Object) of all key/value pairs in map
| map | The map whose contents are to be retrieved. |
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Remove an existing key from the array map.
| key | The key of the mapping to remove. |
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Remove all keys in the array map that exist in the given collection.
| collection | The collection whose contents are to be used to remove keys. |
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Remove the key/value mapping at the given index.
| index | The desired index, must be between 0 and size()-1. |
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Remove all keys in the array map that do not exist in the given collection.
| collection | The collection whose contents are to be used to determine which keys to keep. |
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Set the value at a given index in the array.
| index | The desired index, must be between 0 and size()-1. |
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| value | The new value to store at this index. |
Return the number of items in this array map.
Map.
Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression:
getClass().getName() + '@' + Integer.toHexString(hashCode())
See Writing a useful
toString method
if you intend implementing your own toString method.
This implementation composes a string by iterating over its mappings. If this map contains itself as a key or a value, the string "(this Map)" will appear in its place.
Return the value at the given index in the array.
| index | The desired index, must be between 0 and size()-1. |
|---|
Return a Collection for iterating over and interacting with all values
in the array map.
Note: this is a fairly inefficient way to access the array contents, it requires generating a number of temporary objects and allocates additional state information associated with the container that will remain for the life of the container.