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/*****************************************************************************
 * Copyright 2012 celum Slovakia s r.o.
 *
 * 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 com.celum.dbtool.step;

/**
 * Class holds version information, how version is compared etc.
 * Because version information could be number, composition of numbers,
 * string etc. and could be compared differently, the version is abstract class.
 * You will implement this abstract class for your own version behaviour.
 *
 * The version is mostly parsed via {@link VersionFactory factory} implementation
 * which is singletoned here and used in Version.of() method. For registering
 * another factory impl. use the registerFactory() method.
 *
 * As default version and factory is used {@link LongVersionFactory long}
 * representation.
 *
 * @author Zdenko Vrabel ([email protected])
 */
public abstract class Version implements Comparable{

    /** NULL pattern */
    public static final Version NULL = new Version() {
        @Override
        public int hashCode() {
            return 0;
        }

        @Override
        public int compareTo(Version o) {
            return 0;
        }

        @Override
        public String toString() {
            return "0";
        }
    };

    /** holds the singletoned version factory */
    private static VersionFactory factory = VersionFactory.DEFAULT;

    /**
     * register a new version factory which will parse the version.
     */
    public static void registerVersionFactory(VersionFactory factory) {
        Version.factory = factory;
    }


    /**
     * parse text and convert it to version object. Parsing depends on
     * version factory which one is registered.
     */
    public static Version of(String text)
    {
        return factory.parse(text);
    }


    /**
     * Equals gives these some results like compareTo()
     */
    @Override
    public final boolean equals(Object o)
    {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Version version = (Version) o;
        if (version.compareTo(this) == 0) return true;
        return false;
    }

    /**
     * you have to implement this method with compareTo() as well.
     */
    public abstract int hashCode();

    /**
     * You have to implement this method because it's needed for
     * automatic version update.
     *
     * @return string form of version
     */
    public abstract String toString();

}




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