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Provides common utility functions
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/*
 * Copyright (c) CQSE GmbH
 *
 * 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 org.conqat.lib.commons.enums;

import java.util.HashMap;
import java.util.Map;

/**
 * This class provides a map from enum constant names to its actual enum values.
 * 
 * This can be used instead of EnumUtils.valueOf() (or .valueOf) for performance reasons,
 * especially if the lookup of constant names is expected to fail often. Otherwise
 * EnumUtils.valueOf() (or .valueOf) have a similar performance.
 * 
 * In case of looking up strings that do not exist as enum constant EnumUtils has to catch an
 * IllegalArgumentException which has an even bigger performance impact. This implementation simply
 * returns null if the element is not found without this overhead.
 */
public class EnumValueMap> {

	/** Lookup map from element names to enum values. */
	private final Map nameToValues = new HashMap<>();

	/** Flag that determines whether the name lookup is case sensitive. */
	private final boolean caseSensisitve;

	/** Constructor for a case sensitive map. */
	public EnumValueMap(Class enumType) {
		this(enumType, true);
	}

	/** Constructor. */
	public EnumValueMap(Class enumType, boolean caseSensisitve) {
		this.caseSensisitve = caseSensisitve;
		for (E e : enumType.getEnumConstants()) {
			nameToValues.put(getKey(e.name()), e);
		}
	}

	/** Returns the lookup map key depending on the case-sensitivity. */
	private String getKey(String name) {
		if (caseSensisitve) {
			return name;
		}
		return name.toLowerCase();
	}

	/** Gets the enum value with the given name from an internal lookup map. */
	public E valueOf(String name) {
		return nameToValues.get(getKey(name));
	}
}