/*

 * Copyright (C) 2007-2010 Júlio Vilmar Gesser.

 * Copyright (C) 2011, 2013-2021 The JavaParser Team.

 *

 * This file is part of JavaParser.

 *

 * JavaParser can be used either under the terms of

 * a) the GNU Lesser General Public License as published by

 *     the Free Software Foundation, either version 3 of the License, or

 *     (at your option) any later version.

 * b) the terms of the Apache License

 *

 * You should have received a copy of both licenses in LICENCE.LGPL and

 * LICENCE.APACHE. Please refer to those files for details.

 *

 * JavaParser is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Lesser General Public License for more details.

 */

package com.github.javaparser.ast;

/**

 * A key to a piece of data associated with a {@link Node} at runtime.

 * The key contains type information that can be used to check the

 * type of any user data value for the key when the value is set. DataKey is abstract in order to

 * force the creation of a subtype. That subtype is used to test for identity when looking for the

 * user data because actual object identity would suffer from problems under serialization.

 * So, the correct way to declare a DataKey is like this:

 * <p>

 * <pre>

 * {@code

 * public static final DataKey<Role> ROLE = new DataKey<Role>() { };

 * }

 * </pre>

 * <p>

 * This code was taken from the <a href="http://wicket.apache.org/">Wicket project</a>.

 *

 * @param <T> The type of the object which is stored

 * @see Node#getData(DataKey)

 */

public abstract class DataKey<T> {

    @Override

    public int hashCode() {

        return getClass().hashCode();

    }

    /**

     * @see java.lang.Object#equals(java.lang.Object)

     */

    @Override

    public boolean equals(Object obj) {

        return obj != null && getClass().equals(obj.getClass());

    }

}