org.glassfish.hk2.utilities.general.WeakHashClock Maven / Gradle / Ivy
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package org.glassfish.hk2.utilities.general;
import java.util.Map;
import org.glassfish.hk2.utilities.cache.CacheKeyFilter;
/**
* This is a clock (if non-empty the next verb will always return a new value
* in a cycle) that can also get values in O(1) complexity. This HashClock
* also has Weak key references, so if the key becomes unavailable it
* will not be retrievable from the get operation and the next operation
* will remove it from the clock
*
* @author jwells
*
*/
public interface WeakHashClock {
/**
* Adds the given pair to the clock. It will
* be placed at the current tail of the clock
*
* @param key Must not be null
* @param value May not be null
*/
public void put(K key, V value);
/**
* Gets the given key, returning null
* if not found
*
* @param key The key to search for, may not be null
* @return The value found, or null if not found
*/
public V get(K key);
/**
* Removes the given key from the clock, if found
*
* @param key The key to remove, may not be null
* @return The value removed if found, or null if not found
*/
public V remove(K key);
/**
* Releases all key/value pairs that match the filter
*
* @param filter A non-null filter that can be used
* to delete every key/value pair that matches the filter
*/
public void releaseMatching(CacheKeyFilter filter);
/**
* Returns the number of elements currently
* in the clock. References that have gone
* away because they were weakly referenced
* will not be counted in the size
*
* @return The number of entries currently
* in the clock
*/
public int size();
/**
* Returns the next key/value pair in the clock,
* or null if the clock has no members. This
* will advance the head and tail of the clock
* to the next element. If the WeakReference
* for the returned element is null then this
* element will also have been removed from
* the clock by this operation
*
* @return The next key/value pair in the
*/
public Map.Entry next();
/**
* Sets the clock size back to zero, no entries
*/
public void clear();
/**
* Causes stale references to be cleared from the data
* structures. Since this is a weak clock the references
* can go away at any time, which happens whenever
* any operation has been performed. However, it may be
* the case that no operation will be performed for a while
* and so this method is provided to have a no-op operation
* to call in order to clear out any stale references
*/
public void clearStaleReferences();
/**
* Tells if this WeakHashClock has Weak keys
* @return true if this map has weak keys, true otherwise
*/
public boolean hasWeakKeys();
}