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The Apache Commons JEXL library is an implementation of the JSTL Expression Language with extensions.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.jexl3;

import java.util.Collection;
import java.util.Collections;
import java.util.Map;

/**
 * Caching scripts or templates interface.
 *
 * @param  source
 * @param  script or template
 */
public interface JexlCache {

    /**
     * Returns the cache capacity, the maximum number of elements it can contain.
     *
     * @return the cache capacity
     */
    int capacity();

    /**
     * Clears the cache.
     */
    void clear();

    /**
     * Produces the cache entry set.
     *
     * 
     * For implementations testing only
     * 
     *
     * @return the cache entry list
     */
    default Collection> entries() {
        return Collections.emptyList();
    }

    /**
     * Gets a value from cache.
     *
     * @param key the cache entry key
     * @return the cache entry value
     */
    V get(K key);

    /**
     * Puts a value in cache.
     *
     * @param key    the cache entry key
     * @param script the cache entry value
     * @return the previously associated value if any
     */
    V put(K key, V script);

    /**
     * Returns the cache size, the actual number of elements it contains.
     *
     * @return the cache size
     */
    int size();

    /**
     * A cached reference.
     */
    interface Reference {
        /**
         * Gets the referenced object.
         * @return the referenced object
         */
        Object getCache();

        /**
         * Sets the referenced object.
         * @param cache the referenced object
         */
        void setCache(Object cache);
    }
}