8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 /**
29 * Class {@code Object} is the root of the class hierarchy.
30 * Every class has {@code Object} as a superclass. All objects,
31 * including arrays, implement the methods of this class.
32 *
33 * @author unascribed
34 * @see java.lang.Class
35 * @since 1.0
36 */
37 public class Object {
38
39 private static native void registerNatives();
40 static {
41 registerNatives();
42 }
43
44 /**
45 * Constructs a new object.
46 */
47 public Object() {}
48
49 /**
50 * Returns the runtime class of this {@code Object}. The returned
51 * {@code Class} object is the object that is locked by {@code
52 * static synchronized} methods of the represented class.
53 *
54 * <p><b>The actual result type is {@code Class<? extends |X|>}
55 * where {@code |X|} is the erasure of the static type of the
56 * expression on which {@code getClass} is called.</b> For
57 * example, no cast is required in this code fragment:</p>
58 *
59 * <p>
60 * {@code Number n = 0; }<br>
61 * {@code Class<? extends Number> c = n.getClass(); }
62 * </p>
63 *
64 * @return The {@code Class} object that represents the runtime
65 * class of this object.
66 * @jls 15.8.2 Class Literals
67 */
68 public final native Class<?> getClass();
69
70 /**
71 * Returns a hash code value for the object. This method is
72 * supported for the benefit of hash tables such as those provided by
73 * {@link java.util.HashMap}.
74 * <p>
75 * The general contract of {@code hashCode} is:
76 * <ul>
77 * <li>Whenever it is invoked on the same object more than once during
78 * an execution of a Java application, the {@code hashCode} method
79 * must consistently return the same integer, provided no information
80 * used in {@code equals} comparisons on the object is modified.
81 * This integer need not remain consistent from one execution of an
82 * application to another execution of the same application.
83 * <li>If two objects are equal according to the {@code equals(Object)}
84 * method, then calling the {@code hashCode} method on each of
85 * the two objects must produce the same integer result.
86 * <li>It is <em>not</em> required that if two objects are unequal
87 * according to the {@link java.lang.Object#equals(java.lang.Object)}
88 * method, then calling the {@code hashCode} method on each of the
89 * two objects must produce distinct integer results. However, the
90 * programmer should be aware that producing distinct integer results
91 * for unequal objects may improve the performance of hash tables.
92 * </ul>
93 * <p>
94 * As much as is reasonably practical, the hashCode method defined
95 * by class {@code Object} does return distinct integers for
96 * distinct objects. (The hashCode may or may not be implemented
97 * as some function of an object's memory address at some point
98 * in time.)
99 *
100 * @return a hash code value for this object.
101 * @see java.lang.Object#equals(java.lang.Object)
102 * @see java.lang.System#identityHashCode
103 */
104 public native int hashCode();
105
106 /**
107 * Indicates whether some other object is "equal to" this one.
108 * <p>
109 * The {@code equals} method implements an equivalence relation
110 * on non-null object references:
111 * <ul>
112 * <li>It is <i>reflexive</i>: for any non-null reference value
113 * {@code x}, {@code x.equals(x)} should return
114 * {@code true}.
115 * <li>It is <i>symmetric</i>: for any non-null reference values
116 * {@code x} and {@code y}, {@code x.equals(y)}
117 * should return {@code true} if and only if
118 * {@code y.equals(x)} returns {@code true}.
119 * <li>It is <i>transitive</i>: for any non-null reference values
120 * {@code x}, {@code y}, and {@code z}, if
121 * {@code x.equals(y)} returns {@code true} and
122 * {@code y.equals(z)} returns {@code true}, then
123 * {@code x.equals(z)} should return {@code true}.
196 * is {@code T[]} where T is any reference or primitive type.
197 * Otherwise, this method creates a new instance of the class of this
198 * object and initializes all its fields with exactly the contents of
199 * the corresponding fields of this object, as if by assignment; the
200 * contents of the fields are not themselves cloned. Thus, this method
201 * performs a "shallow copy" of this object, not a "deep copy" operation.
202 * <p>
203 * The class {@code Object} does not itself implement the interface
204 * {@code Cloneable}, so calling the {@code clone} method on an object
205 * whose class is {@code Object} will result in throwing an
206 * exception at run time.
207 *
208 * @return a clone of this instance.
209 * @throws CloneNotSupportedException if the object's class does not
210 * support the {@code Cloneable} interface. Subclasses
211 * that override the {@code clone} method can also
212 * throw this exception to indicate that an instance cannot
213 * be cloned.
214 * @see java.lang.Cloneable
215 */
216 protected native Object clone() throws CloneNotSupportedException;
217
218 /**
219 * Returns a string representation of the object. In general, the
220 * {@code toString} method returns a string that
221 * "textually represents" this object. The result should
222 * be a concise but informative representation that is easy for a
223 * person to read.
224 * It is recommended that all subclasses override this method.
225 * <p>
226 * The {@code toString} method for class {@code Object}
227 * returns a string consisting of the name of the class of which the
228 * object is an instance, the at-sign character `{@code @}', and
229 * the unsigned hexadecimal representation of the hash code of the
230 * object. In other words, this method returns a string equal to the
231 * value of:
232 * <blockquote>
233 * <pre>
234 * getClass().getName() + '@' + Integer.toHexString(hashCode())
235 * </pre></blockquote>
|
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 import jdk.internal.HotSpotIntrinsicCandidate;
29
30 /**
31 * Class {@code Object} is the root of the class hierarchy.
32 * Every class has {@code Object} as a superclass. All objects,
33 * including arrays, implement the methods of this class.
34 *
35 * @author unascribed
36 * @see java.lang.Class
37 * @since 1.0
38 */
39 public class Object {
40
41 private static native void registerNatives();
42 static {
43 registerNatives();
44 }
45
46 /**
47 * Constructs a new object.
48 */
49 @HotSpotIntrinsicCandidate
50 public Object() {}
51
52 /**
53 * Returns the runtime class of this {@code Object}. The returned
54 * {@code Class} object is the object that is locked by {@code
55 * static synchronized} methods of the represented class.
56 *
57 * <p><b>The actual result type is {@code Class<? extends |X|>}
58 * where {@code |X|} is the erasure of the static type of the
59 * expression on which {@code getClass} is called.</b> For
60 * example, no cast is required in this code fragment:</p>
61 *
62 * <p>
63 * {@code Number n = 0; }<br>
64 * {@code Class<? extends Number> c = n.getClass(); }
65 * </p>
66 *
67 * @return The {@code Class} object that represents the runtime
68 * class of this object.
69 * @jls 15.8.2 Class Literals
70 */
71 @HotSpotIntrinsicCandidate
72 public final native Class<?> getClass();
73
74 /**
75 * Returns a hash code value for the object. This method is
76 * supported for the benefit of hash tables such as those provided by
77 * {@link java.util.HashMap}.
78 * <p>
79 * The general contract of {@code hashCode} is:
80 * <ul>
81 * <li>Whenever it is invoked on the same object more than once during
82 * an execution of a Java application, the {@code hashCode} method
83 * must consistently return the same integer, provided no information
84 * used in {@code equals} comparisons on the object is modified.
85 * This integer need not remain consistent from one execution of an
86 * application to another execution of the same application.
87 * <li>If two objects are equal according to the {@code equals(Object)}
88 * method, then calling the {@code hashCode} method on each of
89 * the two objects must produce the same integer result.
90 * <li>It is <em>not</em> required that if two objects are unequal
91 * according to the {@link java.lang.Object#equals(java.lang.Object)}
92 * method, then calling the {@code hashCode} method on each of the
93 * two objects must produce distinct integer results. However, the
94 * programmer should be aware that producing distinct integer results
95 * for unequal objects may improve the performance of hash tables.
96 * </ul>
97 * <p>
98 * As much as is reasonably practical, the hashCode method defined
99 * by class {@code Object} does return distinct integers for
100 * distinct objects. (The hashCode may or may not be implemented
101 * as some function of an object's memory address at some point
102 * in time.)
103 *
104 * @return a hash code value for this object.
105 * @see java.lang.Object#equals(java.lang.Object)
106 * @see java.lang.System#identityHashCode
107 */
108 @HotSpotIntrinsicCandidate
109 public native int hashCode();
110
111 /**
112 * Indicates whether some other object is "equal to" this one.
113 * <p>
114 * The {@code equals} method implements an equivalence relation
115 * on non-null object references:
116 * <ul>
117 * <li>It is <i>reflexive</i>: for any non-null reference value
118 * {@code x}, {@code x.equals(x)} should return
119 * {@code true}.
120 * <li>It is <i>symmetric</i>: for any non-null reference values
121 * {@code x} and {@code y}, {@code x.equals(y)}
122 * should return {@code true} if and only if
123 * {@code y.equals(x)} returns {@code true}.
124 * <li>It is <i>transitive</i>: for any non-null reference values
125 * {@code x}, {@code y}, and {@code z}, if
126 * {@code x.equals(y)} returns {@code true} and
127 * {@code y.equals(z)} returns {@code true}, then
128 * {@code x.equals(z)} should return {@code true}.
201 * is {@code T[]} where T is any reference or primitive type.
202 * Otherwise, this method creates a new instance of the class of this
203 * object and initializes all its fields with exactly the contents of
204 * the corresponding fields of this object, as if by assignment; the
205 * contents of the fields are not themselves cloned. Thus, this method
206 * performs a "shallow copy" of this object, not a "deep copy" operation.
207 * <p>
208 * The class {@code Object} does not itself implement the interface
209 * {@code Cloneable}, so calling the {@code clone} method on an object
210 * whose class is {@code Object} will result in throwing an
211 * exception at run time.
212 *
213 * @return a clone of this instance.
214 * @throws CloneNotSupportedException if the object's class does not
215 * support the {@code Cloneable} interface. Subclasses
216 * that override the {@code clone} method can also
217 * throw this exception to indicate that an instance cannot
218 * be cloned.
219 * @see java.lang.Cloneable
220 */
221 @HotSpotIntrinsicCandidate
222 protected native Object clone() throws CloneNotSupportedException;
223
224 /**
225 * Returns a string representation of the object. In general, the
226 * {@code toString} method returns a string that
227 * "textually represents" this object. The result should
228 * be a concise but informative representation that is easy for a
229 * person to read.
230 * It is recommended that all subclasses override this method.
231 * <p>
232 * The {@code toString} method for class {@code Object}
233 * returns a string consisting of the name of the class of which the
234 * object is an instance, the at-sign character `{@code @}', and
235 * the unsigned hexadecimal representation of the hash code of the
236 * object. In other words, this method returns a string equal to the
237 * value of:
238 * <blockquote>
239 * <pre>
240 * getClass().getName() + '@' + Integer.toHexString(hashCode())
241 * </pre></blockquote>
|