Package io.opentelemetry.instrumentation.api.internal.cache.weaklockfree

Class WeakConcurrentMap<K,V>

java.lang.Object
io.opentelemetry.instrumentation.api.internal.cache.weaklockfree.WeakConcurrentMap<K,V>
All Implemented Interfaces:
Iterable<Map.Entry<K,V>>
Direct Known Subclasses:
WeakConcurrentMap.WithInlinedExpunction
public class WeakConcurrentMap<K,V> extends Object
A thread-safe map with weak keys. Entries are based on a key's system hash code and keys are considered equal only by reference equality. This class does not implement the Map interface because this implementation is incompatible with the map contract. While iterating over a map's entries, any key that has not passed iteration is referenced non-weakly.

This class has been copied as is from https://github.com/raphw/weak-lock-free/blob/ad0e5e0c04d4a31f9485bf12b89afbc9d75473b3/src/main/java/com/blogspot/mydailyjava/weaklockfree/WeakConcurrentMap.java

This class is internal and is hence not for public use. Its APIs are unstable and can change at any time.

  • Constructor Details

    • WeakConcurrentMap

      public WeakConcurrentMap()

    • WeakConcurrentMap

      public WeakConcurrentMap(boolean reuseKeys)
      Parameters:
      reuseKeys - true if the lookup keys should be reused via a ThreadLocal. Note that setting this to true may result in class loader leaks. See isPersistentClassLoader(ClassLoader) for more details.

    • WeakConcurrentMap

      public WeakConcurrentMap(boolean reuseKeys, ConcurrentMap<io.opentelemetry.instrumentation.api.internal.cache.weaklockfree.AbstractWeakConcurrentMap.WeakKey<K>,V> target)
      Parameters:
      reuseKeys - true if the lookup keys should be reused via a ThreadLocal. Note that setting this to true may result in class loader leaks. See isPersistentClassLoader(ClassLoader) for more details.
      target - ConcurrentMap implementation that this class wraps.

  • Method Details

    • getLookupKey

      protected io.opentelemetry.instrumentation.api.internal.cache.weaklockfree.WeakConcurrentMap.LookupKey<K> getLookupKey(K key)
      Override with care as it can cause lookup failures if done incorrectly. The result must have the same Object.hashCode() as the input and be equal to a weak reference of the key. When overriding this, also override resetLookupKey(L).

    • resetLookupKey

      protected void resetLookupKey(io.opentelemetry.instrumentation.api.internal.cache.weaklockfree.WeakConcurrentMap.LookupKey<K> lookupKey)
      Resets any reusable state in the lookup key.

    • get

      @Nullable public V get(K key)
      Parameters:
      key - The key of the entry.
      Returns:
      The value of the entry or the default value if it did not exist.

    • getIfPresent

      @Nullable public V getIfPresent(K key)
      Parameters:
      key - The key of the entry.
      Returns:
      The value of the entry or null if it did not exist.

    • containsKey

      public boolean containsKey(K key)
      Parameters:
      key - The key of the entry.
      Returns:
      true if the key already defines a value.

    • put

      public V put(K key, V value)
      Parameters:
      key - The key of the entry.
      value - The value of the entry.
      Returns:
      The previous entry or null if it does not exist.

    • putIfAbsent

      public V putIfAbsent(K key, V value)
      Parameters:
      key - The key of the entry.
      value - The value of the entry.
      Returns:
      The previous entry or null if it does not exist.

    • computeIfAbsent

      public V computeIfAbsent(K key, Function<? super K,? extends V> mappingFunction)

    • putIfProbablyAbsent

      public V putIfProbablyAbsent(K key, V value)
      Parameters:
      key - The key of the entry.
      value - The value of the entry.
      Returns:
      The previous entry or null if it does not exist.

    • remove

      public V remove(K key)
      Parameters:
      key - The key of the entry.
      Returns:
      The removed entry or null if it does not exist.

    • clear

      public void clear()
      Clears the entire map.

    • defaultValue

      @Nullable protected V defaultValue(K key)
      Creates a default value. There is no guarantee that the requested value will be set as a once it is created in case that another thread requests a value for a key concurrently.
      Parameters:
      key - The key for which to create a default value.
      Returns:
      The default value for a key without value or null for not defining a default value.

    • expungeStaleEntries

      public static void expungeStaleEntries()
      Cleans all unused references.

    • approximateSize

      public int approximateSize()
      Returns the approximate size of this map where the returned number is at least as big as the actual number of entries.
      Returns:
      The minimum size of this map.

    • iterator

      public Iterator<Map.Entry<K,V>> iterator()
      Specified by:
      iterator in interface Iterable<K>

    • toString

      public String toString()
      Overrides:
      toString in class Object