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This API determines the holidays for a given year, country/name and eventually state/region. The holiday data is stored in XML files (one for each country) and will be read from the classpath. You can provide your own holiday calendar XML file or use any of the provided ones. Currently there are 63 countries supported like the following: United States, most european countries, Russia, India, Australia. Besides those there will be more special calendars like currently existing NYSE calendar (New York Stock Exchange).

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/**
 * Copyright 2013 Sven Diedrichsen
 *
 * Licensed 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 de.jollyday.util;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Cache implementation which handles concurrent access to cached values.
 *
 * @param 
 *            the type of cached values
 */
public class Cache {
	/**
	 * Map for caching
	 */
	private final Map cachingMap = new ConcurrentHashMap<>();
	/**
	 * Returns the value defined by the {@link ValueHandler}
	 *
	 * @param valueHandler
	 *            which creates the key and the value if necessary
	 * @return the eventually cached value
	 */
	public VALUE get(ValueHandler valueHandler) {
		final String key = valueHandler.getKey();
		// Try to first get the value which is most likely cached to avoid creating a lambda.
		final VALUE value = cachingMap.get(key);
		return value != null ? value : cachingMap.computeIfAbsent(key, k -> valueHandler.createValue());
	}

	/**
	 * Clears the cache.
	 */
	public void clear() {
		cachingMap.clear();
	}

	public interface ValueHandler {
		String getKey();
		VALUE createValue();
	}

}