| 1 | /* |
|---|---|
| 2 | * Copyright (C) 2007-2010 Júlio Vilmar Gesser. |
| 3 | * Copyright (C) 2011, 2013-2020 The JavaParser Team. |
| 4 | * |
| 5 | * This file is part of JavaParser. |
| 6 | * |
| 7 | * JavaParser can be used either under the terms of |
| 8 | * a) the GNU Lesser General Public License as published by |
| 9 | * the Free Software Foundation, either version 3 of the License, or |
| 10 | * (at your option) any later version. |
| 11 | * b) the terms of the Apache License |
| 12 | * |
| 13 | * You should have received a copy of both licenses in LICENCE.LGPL and |
| 14 | * LICENCE.APACHE. Please refer to those files for details. |
| 15 | * |
| 16 | * JavaParser is distributed in the hope that it will be useful, |
| 17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 19 | * GNU Lesser General Public License for more details. |
| 20 | */ |
| 21 | |
| 22 | package com.github.javaparser.ast; |
| 23 | |
| 24 | /** |
| 25 | * A key to a piece of data associated with a {@link Node} at runtime. |
| 26 | * The key contains type information that can be used to check the |
| 27 | * type of any user data value for the key when the value is set. DataKey is abstract in order to |
| 28 | * force the creation of a subtype. That subtype is used to test for identity when looking for the |
| 29 | * user data because actual object identity would suffer from problems under serialization. |
| 30 | * So, the correct way to declare a DataKey is like this: |
| 31 | * <p> |
| 32 | * <pre> |
| 33 | * {@code |
| 34 | * public static final DataKey<Role> ROLE = new DataKey<Role>() { }; |
| 35 | * } |
| 36 | * </pre> |
| 37 | * <p> |
| 38 | * This code was taken from the <a href="http://wicket.apache.org/">Wicket project</a>. |
| 39 | * |
| 40 | * @param <T> The type of the object which is stored |
| 41 | * @see Node#getData(DataKey) |
| 42 | */ |
| 43 | public abstract class DataKey<T> { |
| 44 | @Override |
| 45 | public int hashCode() { |
| 46 | return getClass().hashCode(); |
| 47 | } |
| 48 | |
| 49 | /** |
| 50 | * @see java.lang.Object#equals(java.lang.Object) |
| 51 | */ |
| 52 | @Override |
| 53 | public boolean equals(Object obj) { |
| 54 | return obj != null && getClass().equals(obj.getClass()); |
| 55 | } |
| 56 | } |
| 57 |