| 1 | // License: GPL. For details, see LICENSE file.
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| 2 | package org.openstreetmap.josm.data.osm;
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| 3 |
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| 4 | /**
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| 5 | * An interface allowing injection of hashcode and equality implementation
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| 6 | * based on some inner state of an object for a set.
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| 7 | * It supports two type parameters to implement effective foreign key implementation
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| 8 | * inside (@link Storage}, but for basic use, both type parameters are the same.
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| 9 | *
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| 10 | * For use cases, see {@link Storage}.
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| 11 | * @author nenik
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| 12 | */
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| 13 | public interface Hash<K,T> {
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| 14 |
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| 15 | /**
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| 16 | * Get hashcode for given instance, based on some inner state of the
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| 17 | * instance. The returned hashcode should remain constant over the time,
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| 18 | * so it should be based on some instance invariant.
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| 19 | *
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| 20 | * @param k the object to compute hashcode for
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| 21 | * @return computed hashcode
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| 22 | */
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| 23 | public int getHashCode(K k);
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| 24 |
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| 25 | /**
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| 26 | * Compare two instances for semantic or lookup equality. For use cases
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| 27 | * where it compares different types, refer to {@link Storage}.
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| 28 | *
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| 29 | * @param k the object to compare
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| 30 | * @param t the object to compare
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| 31 | * @return true if the objects are semantically equivalent, or if k
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| 32 | * uniquely identifies t in given class.
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| 33 | */
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| 34 | public boolean equals(K k, T t);
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| 35 | }
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