Summary: Ctors | Methods | Protected Methods | Inherited Methods | [Expand All]

Added in API level 12

public class

LruCache

extends Object

java.lang.Object
↳	android.util.LruCache<K, V>

Class Overview

A cache that holds strong references to a limited number of values. Each time a value is accessed, it is moved to the head of a queue. When a value is added to a full cache, the value at the end of that queue is evicted and may become eligible for garbage collection.

If your cached values hold resources that need to be explicitly released, override entryRemoved(boolean, K, V, V).

If a cache miss should be computed on demand for the corresponding keys, override create(K). This simplifies the calling code, allowing it to assume a value will always be returned, even when there's a cache miss.

By default, the cache size is measured in the number of entries. Override sizeOf(K, V) to size the cache in different units. For example, this cache is limited to 4MiB of bitmaps:

   int cacheSize = 4 * 1024 * 1024; // 4MiB
   LruCache bitmapCache = new LruCache(cacheSize) {
       protected int sizeOf(String key, Bitmap value) {
           return value.getByteCount();
       
   }}

This class is thread-safe. Perform multiple cache operations atomically by synchronizing on the cache:

   synchronized (cache) {
     if (cache.get(key) == null) {
         cache.put(key, value);
     
   }}

This class does not allow null to be used as a key or value. A return value of null from get(K), put(K, V) or remove(K) is unambiguous: the key was not in the cache.

This class appeared in Android 3.1 (Honeycomb MR1); it's available as part of Android's Support Package for earlier releases.

Summary

Public Constructors
	LruCache(int maxSize)

Public Methods
synchronized final int	createCount() Returns the number of times `create(Object)` returned a value.
final void	evictAll() Clear the cache, calling `entryRemoved(boolean, K, V, V)` on each removed entry.
synchronized final int	evictionCount() Returns the number of values that have been evicted.
final V	get(K key) Returns the value for `key` if it exists in the cache or can be created by `#create`.
synchronized final int	hitCount() Returns the number of times `get(K)` returned a value that was already present in the cache.
synchronized final int	maxSize() For caches that do not override `sizeOf(K, V)`, this returns the maximum number of entries in the cache.
synchronized final int	missCount() Returns the number of times `get(K)` returned null or required a new value to be created.
final V	put(K key, V value) Caches `value` for `key`.
synchronized final int	putCount() Returns the number of times `put(K, V)` was called.
final V	remove(K key) Removes the entry for `key` if it exists.
void	resize(int maxSize) Sets the size of the cache.
synchronized final int	size() For caches that do not override `sizeOf(K, V)`, this returns the number of entries in the cache.
synchronized final Map<K, V>	snapshot() Returns a copy of the current contents of the cache, ordered from least recently accessed to most recently accessed.
synchronized final String	toString() Returns a string containing a concise, human-readable description of this object.
void	trimToSize(int maxSize) Remove the eldest entries until the total of remaining entries is at or below the requested size.

Protected Methods
V	create(K key) Called after a cache miss to compute a value for the corresponding key.
void	entryRemoved(boolean evicted, K key, V oldValue, V newValue) Called for entries that have been evicted or removed.
int	sizeOf(K key, V value) Returns the size of the entry for `key` and `value` in user-defined units.

[Expand]

Inherited Methods

From class java.lang.Object

Object	clone() Creates and returns a copy of this `Object`.
boolean	equals(Object o) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of `Class` that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object.
final void	wait(long millis, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.
final void	wait(long millis) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.

evicted	true if the entry is being removed to make space, false if the removal was caused by a `put(K, V)` or `remove(K)`.
newValue	the new value for `key`, if it exists. If non-null, this removal was caused by a `put(K, V)`. Otherwise it was caused by an eviction or a `remove(K)`.

Results

Interfaces

Classes

Enums

Exceptions

LruCache

Class Overview

Summary

Public Constructors

public LruCache (int maxSize)

Parameters

Public Methods

public final synchronized int createCount ()

public final void evictAll ()

public final synchronized int evictionCount ()

public final V get (K key)

public final synchronized int hitCount ()

public final synchronized int maxSize ()

public final synchronized int missCount ()

public final V put (K key, V value)

Returns

public final synchronized int putCount ()

public final V remove (K key)

Returns

public void resize (int maxSize)

Parameters

public final synchronized int size ()

public final synchronized Map<K, V> snapshot ()

public final synchronized String toString ()

Returns

public void trimToSize (int maxSize)

Parameters

Protected Methods

protected V create (K key)

protected void entryRemoved (boolean evicted, K key, V oldValue, V newValue)

Parameters

protected int sizeOf (K key, V value)