16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.util;
27
28 /**
29 * This class consists of {@code static} utility methods for operating
30 * on objects. These utilities include {@code null}-safe or {@code
31 * null}-tolerant methods for computing the hash code of an object,
32 * returning a string for an object, and comparing two objects.
33 *
34 * @since 1.7
35 */
36 public class Objects {
37 private Objects() {
38 throw new AssertionError("No java.util.Objects instances for you!");
39 }
40
41 /**
42 * Returns {@code true} if the arguments are equal to each other
43 * and {@code false} otherwise.
44 * Consequently, if both arguments are {@code null}, {@code true}
45 * is returned and if exactly one argument is {@code null}, {@code
46 * false} is returned. Otherwise, equality is determined by using
47 * the {@link Object#equals equals} method of the first
48 * argument.
49 *
50 * @param a an object
51 * @param b an object to be compared with {@code a} for equality
52 * @return {@code true} if the arguments are equal to each other
53 * and {@code false} otherwise
54 * @see Object#equals(Object)
55 */
56 public static boolean equals(Object a, Object b) {
57 return (a == b) || (a != null && a.equals(b));
58 }
59
60 /**
61 * Returns the hash code of a non-{@code null} argument and 0 for
62 * a {@code null} argument.
63 *
64 * @param o an object
65 * @return the hash code of a non-{@code null} argument and 0 for
66 * a {@code null} argument
67 * @see Object#hashCode
68 */
69 public static int hashCode(Object o) {
70 return o != null ? o.hashCode() : 0;
71 }
72
73 /**
74 * Returns the result of calling {@code toString} for a non-{@code
75 * null} argument and {@code "null"} for a {@code null} argument.
76 *
77 * @param o an object
78 * @return the result of calling {@code toString} for a non-{@code
79 * null} argument and {@code "null"} for a {@code null} argument
80 * @see Object#toString
81 * @see String#valueOf(Object)
82 */
83 public static String toString(Object o) {
84 return String.valueOf(o);
85 }
86
87 /**
88 * Returns 0 if the arguments are identical and {@code
89 * c.compare(a, b)} otherwise.
90 * Consequently, if both arguments are {@code null} 0
91 * is returned.
92 *
93 * <p>Note that if one of the arguments is {@code null}, a {@code
94 * NullPointerException} may or may not be thrown depending on
95 * what ordering policy, if any, the {@link Comparator Comparator}
96 * chooses to have for {@code null} values.
97 *
98 * @param <T> the type of the objects being compared
99 * @param a an object
100 * @param b an object to be compared with {@code a}
101 * @param c the {@code Comparator} to compare the first two arguments
102 * @return 0 if the arguments are identical and {@code
103 * c.compare(a, b)} otherwise.
104 * @see Comparable
105 * @see Comparator
106 */
107 public static <T> int compare(T a, T b, Comparator<? super T> c) {
|
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.util;
27
28 /**
29 * This class consists of {@code static} utility methods for operating
30 * on objects. These utilities include {@code null}-safe or {@code
31 * null}-tolerant methods for computing the hash code of an object,
32 * returning a string for an object, and comparing two objects.
33 *
34 * @since 1.7
35 */
36 public final class Objects {
37 private Objects() {
38 throw new AssertionError("No java.util.Objects instances for you!");
39 }
40
41 /**
42 * Returns {@code true} if the arguments are equal to each other
43 * and {@code false} otherwise.
44 * Consequently, if both arguments are {@code null}, {@code true}
45 * is returned and if exactly one argument is {@code null}, {@code
46 * false} is returned. Otherwise, equality is determined by using
47 * the {@link Object#equals equals} method of the first
48 * argument.
49 *
50 * @param a an object
51 * @param b an object to be compared with {@code a} for equality
52 * @return {@code true} if the arguments are equal to each other
53 * and {@code false} otherwise
54 * @see Object#equals(Object)
55 */
56 public static boolean equals(Object a, Object b) {
57 return (a == b) || (a != null && a.equals(b));
58 }
59
60 /**
61 * Returns {@code true} if the arguments are deeply equal to each other
62 * and {@code false} otherwise.
63 *
64 * Two {@code null} values are deeply equal. If both arguments are
65 * arrays, the algorithm in {@link Arrays#deepEquals(Object[],
66 * Object[]) Arrays.deepEquals} is used to determine equality.
67 * Otherwise, equality is determined by using the {@link
68 * Object#equals equals} method of the first argument.
69 *
70 * @param a an object
71 * @param b an object to be compared with {@code a} for deep equality
72 * @return {@code true} if the arguments are deeply equal to each other
73 * and {@code false} otherwise
74 * @see Arrays#deepEquals(Object[], Object[])
75 * @see Objects#equals(Object, Object)
76 */
77 public static boolean deepEquals(Object a, Object b) {
78 if (a == b)
79 return true;
80 else if (a == null || b == null)
81 return false;
82 else
83 return Arrays.deepEquals0(a, b);
84 }
85
86 /**
87 * Returns the hash code of a non-{@code null} argument and 0 for
88 * a {@code null} argument.
89 *
90 * @param o an object
91 * @return the hash code of a non-{@code null} argument and 0 for
92 * a {@code null} argument
93 * @see Object#hashCode
94 */
95 public static int hashCode(Object o) {
96 return o != null ? o.hashCode() : 0;
97 }
98
99 /**
100 * Generates a hash code for a sequence of input values. The hash
101 * code is generated as if all the input values were placed into an
102 * array, and that array were hashed by calling {@link
103 * Arrays#hashCode(Object[])}.
104 *
105 * <p>This method is useful for implementing {@link
106 * Object#hashCode()} on objects containing multiple fields. For
107 * example, if an object that has three fields, {@code x}, {@code
108 * y}, and {@code z}, one could write:
109 *
110 * <blockquote><pre>
111 * @Override public int hashCode() {
112 * return Objects.hash(x, y, z);
113 * }
114 * </pre></blockquote>
115 *
116 * <b>Warning: When a single object reference is supplied, the returned
117 * value does not equal the hash code of that object reference.</b> This
118 * value can be computed by calling {@link #hashCode(Object)}.
119 *
120 * @param values the values to be hashed
121 * @return a hash value of the sequence of input values
122 * @see Arrays#hashCode
123 * @see List#hashCode
124 */
125 public static int hash(Object... values) {
126 return Arrays.hashCode(values);
127 }
128
129 /**
130 * Returns the result of calling {@code toString} for a non-{@code
131 * null} argument and {@code "null"} for a {@code null} argument.
132 *
133 * @param o an object
134 * @return the result of calling {@code toString} for a non-{@code
135 * null} argument and {@code "null"} for a {@code null} argument
136 * @see Object#toString
137 * @see String#valueOf(Object)
138 */
139 public static String toString(Object o) {
140 return String.valueOf(o);
141 }
142
143 /**
144 * Returns the result of calling {@code toString} on the first
145 * argument if the first argument is not {@code null} and returns
146 * the second argument otherwise.
147 *
148 * @param o an object
149 * @param nullDefault string to return if the first argument is
150 * {@code null}
151 * @return the result of calling {@code toString} on the first
152 * argument if it is not {@code null} and the second argument
153 * otherwise.
154 * @see Objects#toString(Object)
155 */
156 public static String toString(Object o, String nullDefault) {
157 return (o != null) ? o.toString() : nullDefault;
158 }
159
160 /**
161 * Returns 0 if the arguments are identical and {@code
162 * c.compare(a, b)} otherwise.
163 * Consequently, if both arguments are {@code null} 0
164 * is returned.
165 *
166 * <p>Note that if one of the arguments is {@code null}, a {@code
167 * NullPointerException} may or may not be thrown depending on
168 * what ordering policy, if any, the {@link Comparator Comparator}
169 * chooses to have for {@code null} values.
170 *
171 * @param <T> the type of the objects being compared
172 * @param a an object
173 * @param b an object to be compared with {@code a}
174 * @param c the {@code Comparator} to compare the first two arguments
175 * @return 0 if the arguments are identical and {@code
176 * c.compare(a, b)} otherwise.
177 * @see Comparable
178 * @see Comparator
179 */
180 public static <T> int compare(T a, T b, Comparator<? super T> c) {
|