Package com.ss.android.ugc.bytex.common.utils

Class LruCache<K,​V>

  • public class LruCache<K,​V>
extends java.lang.Object
    Static library version of android.util.LruCache. Used to write apps that run on API levels prior to 12. When running on API level 12 or above, this implementation is still used; it does not try to switch to the framework's implementation. See the framework SDK documentation for a class overview.

    • Constructor Summary

      Constructors 
      Constructor Description
      LruCache​(int maxSize)  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void clear()  
      protected V create​(K key)
      Called after a cache miss to compute a value for the corresponding key.
      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.
      void evictAll()
      Clear the cache, calling entryRemoved(boolean, K, V, V) on each removed entry.
      int evictionCount()
      Returns the number of values that have been evicted.
      V get​(K key)
      Returns the value for key if it exists in the cache or can be created by #create.
      int hitCount()
      Returns the number of times get(K) returned a value that was already present in the cache.
      int maxSize()
      For caches that do not override sizeOf(K, V), this returns the maximum number of entries in the cache.
      int missCount()
      Returns the number of times get(K) returned null or required a new value to be created.
      V put​(K key, V value)
      Caches value for key.
      int putCount()
      Returns the number of times put(K, V) was called.
      V remove​(K key)
      Removes the entry for key if it exists.
      void resize​(int maxSize)
      Sets the size of the cache.
      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.
      java.util.Map<K,​V> snapshot()
      Returns a copy of the current contents of the cache, ordered from least recently accessed to most recently accessed.
      java.lang.String toString()  
      void trimToSize​(int maxSize)
      Remove the eldest entries until the total of remaining entries is at or below the requested size.

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • LruCache

        public LruCache​(int maxSize)
        Parameters:
        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.

    • Method Detail

      • resize

        public void resize​(int maxSize)
        Sets the size of the cache.
        Parameters:
        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.
        Returns:
        the previous value mapped by key.

      • trimToSize

        public void trimToSize​(int maxSize)
        Remove the eldest entries until the total of remaining entries is at or below the requested size.
        Parameters:
        maxSize - the maximum size of the cache before returning. May be -1 to evict even 0-sized elements.

      • remove

        public final V remove​(K key)
        Removes the entry for key if it exists.
        Returns:
        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.

        Parameters:
        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.

      • 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 java.util.Map<K,​V> snapshot()
        Returns a copy of the current contents of the cache, ordered from least recently accessed to most recently accessed.

      • clear

        public void clear()

      • toString

        public final java.lang.String toString()
        Overrides:
        toString in class java.lang.Object