Package io.opentelemetry.context.internal.shaded

Class AbstractWeakConcurrentMap<K,​V,​L>

  • All Implemented Interfaces:
    Iterable<Map.Entry<K,​V>>, Runnable
    Direct Known Subclasses:
    WeakConcurrentMap
    public abstract class AbstractWeakConcurrentMap<K,​V,​L>
extends ReferenceQueue<K>
implements Runnable, Iterable<Map.Entry<K,​V>>
    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 offers an abstract-base implementation that allows to override methods. 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 is used in multiple artifacts in OpenTelemetry and while it is in our internal API, generally backwards compatible changes should not be made to avoid a situation where different versions of OpenTelemetry artifacts become incompatible with each other.

    • Constructor Detail

      • AbstractWeakConcurrentMap

        protected AbstractWeakConcurrentMap()

    • Method Detail

      • getLookupKey

        protected abstract L 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 abstract void resetLookupKey​(L lookupKey)
        Resets any reusable state in the lookup key.

      • get

        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

        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.

      • 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

        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 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.

      • run

        public void run()
        Specified by:
        run in interface Runnable