org.beetl.core.util.LruCache<K,V>

public class LruCache<K,V> extends Object

BEGIN LAYOUTLIB CHANGE This is a custom version that doesn't use the non standard LinkedHashMap#eldest. END LAYOUTLIB CHANGE 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<String, Bitmap> bitmapCache = new LruCache<String, Bitmap>(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.

构造器概要

构造器

构造器

说明

LruCache(int maxSize)
方法概要

修饰符和类型

方法

说明

protected V

create(K key)

Called after a cache miss to compute a value for the corresponding key.

final int

createCount()

Returns the number of times create(Object) returned a value.

protected void

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

Called for entries that have been evicted or removed.

final void

evictAll()

Clear the cache, calling entryRemoved(boolean, K, V, V) on each removed entry.

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.

final int

hitCount()

Returns the number of times get(K) returned a value that was already present in the cache.

final int

maxSize()

For caches that do not override sizeOf(K, V), this returns the maximum number of entries in the cache.

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.

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.

final int

size()

For caches that do not override sizeOf(K, V), this returns the number of entries in the cache.

protected int

sizeOf(K key, V value)

Returns the size of the entry for key and value in user-defined units.

final Map<K,V>

snapshot()

Returns a copy of the current contents of the cache, ordered from least recently accessed to most recently accessed.

final String

toString()

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

构造器详细资料
- LruCache
  
  public LruCache(int maxSize)
  
  参数:
  
  maxSize - for caches that do not override sizeOf(K, V), this is the maximum number of entries in the cache. For all other caches, this is the maximum sum of the sizes of the entries in this cache.
方法详细资料
- resize
  
  public void resize(int maxSize)
  
  Sets the size of the cache.
  
  参数:
  
  maxSize - The new maximum size.
- get
  
  public final V get(K key)
  
  Returns the value for key if it exists in the cache or can be created by #create. If a value was returned, it is moved to the head of the queue. This returns null if a value is not cached and cannot be created.
- put
  
  public final V put(K key, V value)
  
  Caches value for key. The value is moved to the head of the queue.
  
  返回:
  
  the previous value mapped by key.
- remove
  
  public final V remove(K key)
  
  Removes the entry for key if it exists.
  
  返回:
  
  the previous value mapped by key.
- entryRemoved
  
  protected void entryRemoved(boolean evicted, K key, V oldValue, V newValue)
  
  Called for entries that have been evicted or removed. This method is invoked when a value is evicted to make space, removed by a call to remove(K), or replaced by a call to put(K, V). The default implementation does nothing.
  The method is called without synchronization: other threads may access the cache while this method is executing.
  
  参数:
  
  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).
- create
  
  protected V create(K key)
  
  Called after a cache miss to compute a value for the corresponding key. Returns the computed value or null if no value can be computed. The default implementation returns null.
  The method is called without synchronization: other threads may access the cache while this method is executing.
  If a value for key exists in the cache when this method returns, the created value will be released with entryRemoved(boolean, K, V, V) and discarded. This can occur when multiple threads request the same key at the same time (causing multiple values to be created), or when one thread calls put(K, V) while another is creating a value for the same key.
- sizeOf
  
  protected int sizeOf(K key, V value)
  
  Returns the size of the entry for key and value in user-defined units. The default implementation returns 1 so that size is the number of entries and max size is the maximum number of entries.
  An entry's size must not change while it is in the cache.
- evictAll
  
  public final void evictAll()
  
  Clear the cache, calling entryRemoved(boolean, K, V, V) on each removed entry.
- size
  
  public final int size()
  
  For caches that do not override sizeOf(K, V), this returns the number of entries in the cache. For all other caches, this returns the sum of the sizes of the entries in this cache.
- maxSize
  
  public final int maxSize()
  
  For caches that do not override sizeOf(K, V), this returns the maximum number of entries in the cache. For all other caches, this returns the maximum sum of the sizes of the entries in this cache.
- hitCount
  
  public final int hitCount()
  
  Returns the number of times get(K) returned a value that was already present in the cache.
- missCount
  
  public final int missCount()
  
  Returns the number of times get(K) returned null or required a new value to be created.
- createCount
  
  public final int createCount()
  
  Returns the number of times create(Object) returned a value.
- putCount
  
  public final int putCount()
  
  Returns the number of times put(K, V) was called.
- evictionCount
  
  public final int evictionCount()
  
  Returns the number of values that have been evicted.
- snapshot
  
  public final Map<K,V> snapshot()
  
  Returns a copy of the current contents of the cache, ordered from least recently accessed to most recently accessed.
- toString
  
  public final String toString()
  
  覆盖:
  
  toString 在类中 Object

类 LruCache<K,V>

构造器概要

方法概要

从类继承的方法 java.lang.Object

构造器详细资料

LruCache

方法详细资料

resize

get

put

remove

entryRemoved

create

sizeOf

evictAll

size

maxSize

hitCount

missCount

createCount

putCount

evictionCount

snapshot

toString