Package com.cedarsoftware.util.cache

Class ThreadedLRUCacheStrategy<K,V>

java.lang.Object
com.cedarsoftware.util.cache.ThreadedLRUCacheStrategy<K,V>
Type Parameters:
K - the type of keys maintained by this cache
V - the type of mapped values
All Implemented Interfaces:
Closeable, AutoCloseable, Map<K,V>
public class ThreadedLRUCacheStrategy<K,V> extends Object implements Map<K,V>, Closeable
This class provides a thread-safe Least Recently Used (LRU) cache API that evicts the least recently used items once a threshold is met. It implements the Map interface for convenience.

The Threaded strategy allows for O(1) access for get(), put(), and remove() without blocking. It uses a ConcurrentHashMapNullSafe internally. A single shared background task periodically checks all cache instances and removes the least recently used items from any cache that exceeds its capacity.

LRUCache supports null for both key and value.

Architecture: All ThreadedLRUCacheStrategy instances share a single cleanup thread that runs periodically. Each cache registers itself via a WeakReference, allowing garbage collection of unused caches. The shared task automatically removes dead references during iteration. This design prevents task accumulation under heavy load and ensures efficient resource usage regardless of how many cache instances are created.

Lifecycle: Caches are automatically managed via WeakReferences. Calling close() or shutdown() explicitly removes the cache from the shared cleanup task. If not explicitly closed, the cache will be cleaned up when garbage collected.

Author:
John DeRegnaucourt ([email protected])
Copyright (c) Cedar Software LLC

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

License

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

  • Constructor Details

    • ThreadedLRUCacheStrategy

      public ThreadedLRUCacheStrategy(int capacity)
      Create a ThreadedLRUCacheStrategy with the specified capacity. A shared background task monitors all cache instances and performs cleanup as needed.
      Parameters:
      capacity - int maximum size for the LRU cache.

    • ThreadedLRUCacheStrategy

      @Deprecated public ThreadedLRUCacheStrategy(int capacity, int cleanupDelayMillis)
      Deprecated.
      Use ThreadedLRUCacheStrategy(int) instead. The cleanupDelayMillis parameter is ignored.
      Create a ThreadedLRUCacheStrategy with the specified capacity.

      Note: The cleanupDelayMillis parameter is deprecated and ignored. All cache instances now share a single cleanup task with a fixed interval.

      Parameters:
      capacity - int maximum size for the LRU cache.
      cleanupDelayMillis - ignored (formerly: milliseconds before scheduling cleanup)

  • Method Details

    • shutdown

      public void shutdown()
      Shuts down this cache, removing it from the shared cleanup task. After calling this method, the cache will no longer perform automatic cleanup. Equivalent to calling close().

    • forceCleanup

      public void forceCleanup()
      Forces an immediate cleanup of this cache. This is primarily for testing purposes.

    • close

      public void close()
      Closes this cache, removing it from the shared cleanup task. This method is idempotent - calling it multiple times has no additional effect.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable

    • getCapacity

      public int getCapacity()
      Returns:
      the maximum number of entries in the cache.

    • get

      public V get(Object key)
      Specified by:
      get in interface Map<K,V>

    • put

      public V put(K key, V value)
      Specified by:
      put in interface Map<K,V>

    • putAll

      public void putAll(Map<? extends K,? extends V> m)
      Specified by:
      putAll in interface Map<K,V>

    • isEmpty

      public boolean isEmpty()
      Specified by:
      isEmpty in interface Map<K,V>

    • remove

      public V remove(Object key)
      Specified by:
      remove in interface Map<K,V>

    • computeIfAbsent

      public V computeIfAbsent(K key, Function<? super K,? extends V> mappingFunction)
      Specified by:
      computeIfAbsent in interface Map<K,V>

    • putIfAbsent

      public V putIfAbsent(K key, V value)
      Specified by:
      putIfAbsent in interface Map<K,V>

    • clear

      public void clear()
      Specified by:
      clear in interface Map<K,V>

    • size

      public int size()
      Specified by:
      size in interface Map<K,V>

    • containsKey

      public boolean containsKey(Object key)
      Specified by:
      containsKey in interface Map<K,V>

    • containsValue

      public boolean containsValue(Object value)
      Specified by:
      containsValue in interface Map<K,V>

    • entrySet

      public Set<Map.Entry<K,V>> entrySet()
      Specified by:
      entrySet in interface Map<K,V>

    • keySet

      public Set<K> keySet()
      Specified by:
      keySet in interface Map<K,V>

    • values

      public Collection<V> values()
      Specified by:
      values in interface Map<K,V>

    • equals

      public boolean equals(Object o)
      Specified by:
      equals in interface Map<K,V>
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Specified by:
      hashCode in interface Map<K,V>
      Overrides:
      hashCode in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object