// License: GPL. For details, see LICENSE file.
package org.openstreetmap.josm.data.osm;
/**
* An interface allowing injection of hashcode and equality implementation
* based on some inner state of an object for a set.
* It supports two type parameters to implement effective foreign key implementation
* inside (@link Storage}, but for basic use, both type parameters are the same.
*
* For use cases, see {@link Storage}.
* @author nenik
* @param <K> type for hashCode and first equals parameter
* @param <T> type for second equals parameter
*/
public interface Hash<K, T> {
/**
* Get hashcode for given instance, based on some inner state of the
* instance. The returned hashcode should remain constant over the time,
* so it should be based on some instance invariant.
*
* @param k the object to compute hashcode for
* @return computed hashcode
*/
int getHashCode(K k);
/**
* Compare two instances for semantic or lookup equality. For use cases
* where it compares different types, refer to {@link Storage}.
*
* @param k the object to compare
* @param t the object to compare
* @return true if the objects are semantically equivalent, or if k
* uniquely identifies t in given class.
*/
boolean equals(K k, T t);
}