ConversionComparator.java revision 1551:f3b883bec2d0 
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26/*
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32 */
33/*
34   Copyright 2009-2013 Attila Szegedi
35
36   Licensed under both the Apache License, Version 2.0 (the "Apache License")
37   and the BSD License (the "BSD License"), with licensee being free to
38   choose either of the two at their discretion.
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40   You may not use this file except in compliance with either the Apache
41   License or the BSD License.
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48           http://www.apache.org/licenses/LICENSE-2.0
49
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56   If you choose to use this file in compliance with the BSD License, the
57   following notice applies to you:
58
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82*/
83
84package jdk.dynalink.linker;
85
86
87/**
88 * Optional interface to be implemented by {@link GuardingTypeConverterFactory}
89 * implementers. Language-specific conversions can cause increased overloaded
90 * method resolution ambiguity, as many methods can become applicable because of
91 * additional conversions. The static way of selecting the "most specific"
92 * method will fail more often, because there will be multiple maximally
93 * specific method with unrelated signatures. In these cases, language runtimes
94 * can be asked to resolve the ambiguity by expressing preferences for one
95 * conversion over the other.
96 */
97public interface ConversionComparator {
98    /**
99     * Enumeration of possible outcomes of comparing one conversion to another.
100     */
101    enum Comparison {
102        /** The conversions cannot be compared. **/
103        INDETERMINATE,
104        /** The first conversion is better than the second one. **/
105        TYPE_1_BETTER,
106        /** The second conversion is better than the first one. **/
107        TYPE_2_BETTER,
108    }
109
110    /**
111     * Determines which of the two target types is the preferred conversion
112     * target from a source type.
113     * @param sourceType the source type.
114     * @param targetType1 one potential target type
115     * @param targetType2 another potential target type.
116     * @return one of Comparison constants that establish which - if any - of
117     * the target types is preferred for the conversion.
118     */
119    public Comparison compareConversion(Class<?> sourceType, Class<?> targetType1, Class<?> targetType2);
120}
121