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.misc.Blocker;
29 import jdk.internal.vm.annotation.IntrinsicCandidate;
30
31 /**
32 * Class {@code Object} is the root of the class hierarchy.
33 * Every class has {@code Object} as a superclass. All objects,
34 * including arrays, implement the methods of this class.
35 *
36 * @see java.lang.Class
37 * @since 1.0
38 */
39 public class Object {
40
41 /**
42 * Constructs a new object.
43 */
44 @IntrinsicCandidate
45 public Object() {}
46
47 /**
48 * Returns the runtime class of this {@code Object}. The returned
49 * {@code Class} object is the object that is locked by {@code
50 * static synchronized} methods of the represented class.
51 *
52 * <p><b>The actual result type is {@code Class<? extends |X|>}
53 * where {@code |X|} is the erasure of the static type of the
54 * expression on which {@code getClass} is called.</b> For
223 * that override the {@code clone} method can also
224 * throw this exception to indicate that an instance cannot
225 * be cloned.
226 * @see java.lang.Cloneable
227 */
228 @IntrinsicCandidate
229 protected native Object clone() throws CloneNotSupportedException;
230
231 /**
232 * Returns a string representation of the object.
233 * @apiNote
234 * In general, the
235 * {@code toString} method returns a string that
236 * "textually represents" this object. The result should
237 * be a concise but informative representation that is easy for a
238 * person to read.
239 * It is recommended that all subclasses override this method.
240 * The string output is not necessarily stable over time or across
241 * JVM invocations.
242 * @implSpec
243 * The {@code toString} method for class {@code Object}
244 * returns a string consisting of the name of the class of which the
245 * object is an instance, the at-sign character `{@code @}', and
246 * the unsigned hexadecimal representation of the hash code of the
247 * object. In other words, this method returns a string equal to the
248 * value of:
249 * <blockquote>
250 * <pre>
251 * getClass().getName() + '@' + Integer.toHexString(hashCode())
252 * </pre></blockquote>
253 *
254 * @return a string representation of the object.
255 */
256 public String toString() {
257 return getClass().getName() + "@" + Integer.toHexString(hashCode());
258 }
259
260 /**
261 * Wakes up a single thread that is waiting on this object's
262 * monitor. If any threads are waiting on this object, one of them
263 * is chosen to be awakened. The choice is arbitrary and occurs at
264 * the discretion of the implementation. A thread waits on an object's
265 * monitor by calling one of the {@code wait} methods.
266 * <p>
267 * The awakened thread will not be able to proceed until the current
268 * thread relinquishes the lock on this object. The awakened thread will
269 * compete in the usual manner with any other threads that might be
270 * actively competing to synchronize on this object; for example, the
271 * awakened thread enjoys no reliable privilege or disadvantage in being
272 * the next thread to lock this object.
|
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.misc.Blocker;
29 import jdk.internal.vm.annotation.IntrinsicCandidate;
30 import jdk.internal.access.SharedSecrets;
31
32 import java.util.Objects;
33
34 /**
35 * Class {@code Object} is the root of the class hierarchy.
36 * Every class has {@code Object} as a superclass. All objects,
37 * including arrays, implement the methods of this class.
38 * <p>
39 * Subclasses of {@code java.lang.Object} can be either {@linkplain Class#isIdentity() identity classes}
40 * or {@linkplain Class#isValue value classes}.
41 * The class {@code Object} itself is neither an identity class nor a value class.
42 * See {@jls The Java Language Specification 8.1.1.5 identity and value Classes}.
43 * An instance can be created with {@code new Object()}, those instances are
44 * {@link Objects#isIdentityObject(Object) an identity object}.
45 *
46 * @see java.lang.Class
47 * @since 1.0
48 */
49 public class Object {
50
51 /**
52 * Constructs a new object.
53 */
54 @IntrinsicCandidate
55 public Object() {}
56
57 /**
58 * Returns the runtime class of this {@code Object}. The returned
59 * {@code Class} object is the object that is locked by {@code
60 * static synchronized} methods of the represented class.
61 *
62 * <p><b>The actual result type is {@code Class<? extends |X|>}
63 * where {@code |X|} is the erasure of the static type of the
64 * expression on which {@code getClass} is called.</b> For
233 * that override the {@code clone} method can also
234 * throw this exception to indicate that an instance cannot
235 * be cloned.
236 * @see java.lang.Cloneable
237 */
238 @IntrinsicCandidate
239 protected native Object clone() throws CloneNotSupportedException;
240
241 /**
242 * Returns a string representation of the object.
243 * @apiNote
244 * In general, the
245 * {@code toString} method returns a string that
246 * "textually represents" this object. The result should
247 * be a concise but informative representation that is easy for a
248 * person to read.
249 * It is recommended that all subclasses override this method.
250 * The string output is not necessarily stable over time or across
251 * JVM invocations.
252 * @implSpec
253 * If this object is an instance of an identity class, then
254 * the {@code toString} method for class {@code Object}
255 * returns a string consisting of the name of the class of which the
256 * object is an instance, the at-sign character `{@code @}', and
257 * the unsigned hexadecimal representation of the hash code of the
258 * object. In other words, this method returns a string equal to the
259 * value of:
260 * <blockquote>
261 * <pre>
262 * getClass().getName() + '@' + Integer.toHexString(hashCode())
263 * </pre></blockquote>
264 * <p>
265 * If this object is an instance of a primitive class, then
266 * the {@code toString} method returns a string which contains
267 * the name of the primitive class, and string representations of
268 * all its fields. The precise format produced by this method
269 * is unspecified and subject to change.
270 *
271 * @return a string representation of the object.
272 */
273 public String toString() {
274 return getClass().getName() + "@" + Integer.toHexString(hashCode());
275 }
276
277 /**
278 * Wakes up a single thread that is waiting on this object's
279 * monitor. If any threads are waiting on this object, one of them
280 * is chosen to be awakened. The choice is arbitrary and occurs at
281 * the discretion of the implementation. A thread waits on an object's
282 * monitor by calling one of the {@code wait} methods.
283 * <p>
284 * The awakened thread will not be able to proceed until the current
285 * thread relinquishes the lock on this object. The awakened thread will
286 * compete in the usual manner with any other threads that might be
287 * actively competing to synchronize on this object; for example, the
288 * awakened thread enjoys no reliable privilege or disadvantage in being
289 * the next thread to lock this object.
|