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package org.javimmutable.collections;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

/**
 * Interface for containers that associate keys with values.
 *
 * @param 
 * @param 
 */
public interface Mapped
{
    /**
     * Return the value associated with key or null if no value is associated.
     * Note that if null is an acceptable value to the container then this method
     * will be ambiguous and find() should be used instead.
     *
     * @param key identifies the value to retrieve
     * @return value associated with key or null if no value is associated
     */
    @Nullable
    V get(K key);

    /**
     * Return the value associated with key or defaultValue if no value is associated.
     * Note that if defaultValue is an acceptable value to the container then this method
     * will be ambiguous and find() should be used instead.
     *
     * @param key          identifies the value to retrieve
     * @param defaultValue value to return if no entry exists for key
     * @return value associated with key or defaultValue if no value is associated
     */
    V getValueOr(K key,
                 V defaultValue);

    /**
     * Return a Holder containing the value associated wth the key or an empty
     * Holder if no value is associated with the key.
     *
     * @param key identifies the value to retrieve
     * @return possibly empty Holder containing any value associated with the key
     */
    @Nonnull
    Holder find(K key);
}