| 1 | /*
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| 2 | * JOSMng - a Java Open Street Map editor, the next generation.
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| 3 | *
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| 4 | * Copyright (C) 2008 Petr Nejedly <P.Nejedly@sh.cvut.cz>
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| 5 | *
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| 6 | * This program is free software; you can redistribute it and/or modify
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| 7 | * it under the terms of the GNU General Public License as published by
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| 8 | * the Free Software Foundation; either version 2 of the License, or
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| 9 | * (at your option) any later version.
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| 10 | *
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| 11 | * This program is distributed in the hope that it will be useful,
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| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 14 | * GNU General Public License for more details.
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| 15 |
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| 16 | * You should have received a copy of the GNU General Public License along
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| 17 | * with this program; if not, write to the Free Software Foundation, Inc.,
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| 18 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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| 19 | */
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| 20 |
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| 21 | package org.openstreetmap.josm.data.osm;
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| 22 |
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| 23 | /**
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| 24 | * An interface allowing injection of hashcode and equality implementation
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| 25 | * based on some inner state of an object for a set.
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| 26 | * It supports two type parameters to implement effective foreign key implementation
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| 27 | * inside (@link Storage}, but for basic use, both type parameters are the same.
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| 28 | *
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| 29 | * For use cases, see {@link Storage}.
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| 30 | * @author nenik
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| 31 | */
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| 32 | public interface Hash<K,T> {
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| 33 |
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| 34 | /**
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| 35 | * Get hashcode for given instance, based on some inner state of the
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| 36 | * instance. The returned hashcode should remain constant over the time,
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| 37 | * so it should be based on some instance invariant.
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| 38 | *
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| 39 | * @param k the object to compute hashcode for
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| 40 | * @return computed hashcode
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| 41 | */
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| 42 | public int getHashCode(K k);
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| 43 |
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| 44 | /**
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| 45 | * Compare two instances for semantic or lookup equality. For use cases
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| 46 | * where it compares different types, refer to {@link Storage}.
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| 47 | *
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| 48 | * @param k the object to compare
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| 49 | * @param t the object to compare
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| 50 | * @return true if the objects are semantically equivalent, or if k
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| 51 | * uniquely identifies t in given class.
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| 52 | */
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| 53 | public boolean equals(K k, T t);
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| 54 | }
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