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Copy-on-write collections for easy, thread-safe, immutability

There is a newer version: 1.0.0

package com.github.grignaak.collections;

import java.util.Map;

/**
 * A Copy-On-Write map (or a persistent data structure in the literature.
 *
 * A Copy-On-Write map has a cheap {@link #fork()} method which will return a new instance of the map,
 * but likely sharing the underlying data structure. Even when the data structure is shared, writes to either of the
 * forks are not reflected in the other fork. Forking can happen any number of times.
 *
 * The major purpose of a copy-on-write map is thread safety. A common idiom is to make updates to the collection in
 * one thread and then publish its fork to any number of reader threads. These reader threads can safely read their copy
 * of the fork while concurrent updates are happening.
 */
public interface CowMap extends Map, Forkable {
    /**
     * Create an independent copy of this map, where mutations on the returned instance do not affect this instance
     * and vice versa. Typically uses structural sharing on larger maps.
     */
    CowMap fork();
}