Cardinality.java

/*
 * Copyright 2007 - 2017 the original author or authors.
 *
 * 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 net.sf.jailer.datamodel;


/**
 * Enumeration of association's cardinalities.
 * 
 * @author Ralf Wisser
 */
public enum Cardinality {
	
	ONE_TO_ONE("1:1"),
	ONE_TO_MANY("1:n"),
	MANY_TO_ONE("n:1"),
	MANY_TO_MANY("n:m"); 

	/**
	 * The name of the cardinality.
	 */
	private final String name;
	
	/**
	 * Constructor.
	 * 
	 * @param name the name of the cardinality
	 */
	private Cardinality(String name) {
		this.name = name;
	}

	/**
	 * Gets the cardinality of the reversal association.
	 * 
	 * @return the cardinality of the reversal association
	 */
	public Cardinality reverse() {
		if (this == ONE_TO_ONE) return ONE_TO_ONE;
		if (this == ONE_TO_MANY) return MANY_TO_ONE;
		if (this == MANY_TO_ONE) return ONE_TO_MANY;
		if (this == MANY_TO_MANY) return MANY_TO_MANY;
		return null;
	}

	/**
	 * Parses a stringified cardinality.
	 * 
	 * @param cardinality cardinality name
	 * @return cardinality with given name
	 */
	public static Cardinality parse(String cardinality) {
		if (cardinality == null || "".equals(cardinality)) {
			return null;
		}
		for (Cardinality card: Cardinality.values()) {
			if (card.name.equalsIgnoreCase(cardinality)) {
				return card;
			}
		}
		throw new RuntimeException("unknown cardinality: " + cardinality);
	}
	
	/**
	 * Stringifies cardinality.
	 */
	public String toString() {
		return name;
	}
	
}