Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||
Objects |
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Objects$1 |
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Objects$EqualTo |
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Objects$IsA |
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Objects$SameAs |
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1 | /* | |
2 | Copyright 2004-2008 Paul R. Holser, Jr. All rights reserved. | |
3 | Licensed under the Academic Free License version 3.0 | |
4 | */ | |
5 | ||
6 | package jaggregate; | |
7 | ||
8 | import static jaggregate.internal.ArgumentChecks.*; | |
9 | ||
10 | /** | |
11 | * Utility class that offers useful operations on objects in general. | |
12 | * | |
13 | * @author <a href="mailto:pholser@alumni.rice.edu">Paul Holser</a> | |
14 | * @version $Id: Objects.java,v 1.6 2008/10/03 19:01:23 pholser Exp $ | |
15 | */ | |
16 | public class Objects { | |
17 | private static final String SAME_VALUE_TEMPLATE = "<%1$s>"; | |
18 | ||
19 | /** | |
20 | * Discourages instantiation. | |
21 | * | |
22 | * @throws UnsupportedOperationException always | |
23 | */ | |
24 | 1 | protected Objects() { |
25 | 1 | throw new UnsupportedOperationException(); |
26 | } | |
27 | ||
28 | /** | |
29 | * Tells whether two object references are considered | |
30 | * {@linkplain #equals(Object) equivalent}. Both references can be {@code null}. | |
31 | * | |
32 | * @param first first reference | |
33 | * @param second second reference | |
34 | * @return result of {@code first == null ? second == null : first.equals(second)} | |
35 | */ | |
36 | public static boolean areEqual( Object first, Object second ) { | |
37 | 21259 | return first == null ? second == null : first.equals( second ); |
38 | } | |
39 | ||
40 | /** | |
41 | * Answers a {@linkplain #hashCode() hash value} for the given target object. | |
42 | * | |
43 | * @param target the target object | |
44 | * @return {@code target}'s hash value, or {@code 0} if {@code target} is {@code | |
45 | * null} | |
46 | */ | |
47 | public static int nullSafeHashCode( Object target ) { | |
48 | 14229 | return target == null ? 0 : target.hashCode(); |
49 | } | |
50 | ||
51 | /** | |
52 | * Answers the {@linkplain #toString() string representation} for the target object, | |
53 | * as {@link Object}'s implementation would compute it, disregarding overrides. | |
54 | * | |
55 | * @param target the target object | |
56 | * @return the default string representation for {@code target} | |
57 | */ | |
58 | public static String identityToString( Object target ) { | |
59 | 37 | if ( target == null ) |
60 | 7 | return String.valueOf( target ); |
61 | ||
62 | 30 | return new StringBuilder( target.getClass().getName() ) |
63 | .append( '@' ) | |
64 | .append( Integer.toHexString( target.hashCode() ) ) | |
65 | .toString(); | |
66 | } | |
67 | ||
68 | /** | |
69 | * Answers a predicate which will answer {@code true} if its argument compares | |
70 | * {@linkplain Object#equals(Object) equivalent} to the given comparand. | |
71 | * | |
72 | * @param comparand the comparand to use with the returned predicate | |
73 | * @return a predicate that can be used to compare arguments with {@code comparand} | |
74 | */ | |
75 | public static UnaryPredicate<Object> equalTo( Object comparand ) { | |
76 | 66 | return new EqualTo().bindSecond( comparand ); |
77 | } | |
78 | ||
79 | /** | |
80 | * Answers a predicate which will answer {@code true} if its argument refers to the | |
81 | * same object as the given comparand. | |
82 | * | |
83 | * @param comparand the comparand to use with the returned predicate | |
84 | * @return a predicate that can be used to compare arguments with {@code comparand} | |
85 | */ | |
86 | public static UnaryPredicate<Object> sameAs( Object comparand ) { | |
87 | 9 | return new SameAs().bindSecond( comparand ); |
88 | } | |
89 | ||
90 | /** | |
91 | * Answers a predicate which will answer {@code true} if its argument is an | |
92 | * instance of the given comparand class. | |
93 | * | |
94 | * @param comparand the comparand to use with the returned predicate | |
95 | * @return a predicate that can be used to compare arguments with {@code comparand} | |
96 | * @throws NullPointerException if {@code comparand} is {@code null} | |
97 | */ | |
98 | public static UnaryPredicate<Object> isA( Class<?> comparand ) { | |
99 | 9 | ensureNotNull( comparand, "comparand class" ); |
100 | ||
101 | 8 | return new IsA().bindSecond( comparand ); |
102 | } | |
103 | ||
104 | /** | |
105 | * Answers a predicate which will answer {@code true} if its argument is a class in | |
106 | * the hierarchy of the given object's class. | |
107 | * | |
108 | * @param instance the comparand to use with the returned predicate | |
109 | * @return a predicate that can be used to compare arguments with {@code instance} | |
110 | */ | |
111 | public static UnaryPredicate<Class<?>> classifies( Object instance ) { | |
112 | 7 | return new IsA().bindFirst( instance ); |
113 | } | |
114 | ||
115 | 132 | private static class EqualTo extends BinaryPredicate<Object, Object> { |
116 | public boolean matches( Object first, Object second ) { | |
117 | 331 | return areEqual( first, second ); |
118 | } | |
119 | ||
120 | @Override | |
121 | protected String getFirstBoundDescription() { | |
122 | 1 | return SAME_VALUE_TEMPLATE; |
123 | } | |
124 | } | |
125 | ||
126 | 18 | private static class SameAs extends BinaryPredicate<Object, Object> { |
127 | public boolean matches( Object first, Object second ) { | |
128 | 9 | return first == second; |
129 | } | |
130 | ||
131 | @Override | |
132 | protected String getFirstBoundDescription() { | |
133 | 3 | return SAME_VALUE_TEMPLATE; |
134 | } | |
135 | } | |
136 | ||
137 | 43 | private static class IsA extends BinaryPredicate<Object, Class<?>> { |
138 | public boolean matches( Object first, Class<?> second ) { | |
139 | 13 | return second.isInstance( first ); |
140 | } | |
141 | ||
142 | @Override | |
143 | protected String getFirstBoundDescription() { | |
144 | 1 | return "a class of which <%1$s> is an instance"; |
145 | } | |
146 | ||
147 | @Override | |
148 | protected String getSecondBoundDescription() { | |
149 | 1 | return "an instance of <%1$s>"; |
150 | } | |
151 | } | |
152 | } |