< prev index next >

src/java.base/share/classes/java/lang/Object.java

Print this page

  1 /*
  2  * Copyright (c) 1994, 2021, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.  Oracle designates this
  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.vm.annotation.IntrinsicCandidate;



 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  * @see     java.lang.Class
 36  * @since   1.0
 37  */
 38 public class Object {
 39 
 40     /**
 41      * Constructs a new object.
 42      */
 43     @IntrinsicCandidate
 44     public Object() {}
 45 
 46     /**
 47      * Returns the runtime class of this {@code Object}. The returned
 48      * {@code Class} object is the object that is locked by {@code

222      *               that override the {@code clone} method can also
223      *               throw this exception to indicate that an instance cannot
224      *               be cloned.
225      * @see java.lang.Cloneable
226      */
227     @IntrinsicCandidate
228     protected native Object clone() throws CloneNotSupportedException;
229 
230     /**
231      * Returns a string representation of the object.
232      * @apiNote
233      * In general, the
234      * {@code toString} method returns a string that
235      * "textually represents" this object. The result should
236      * be a concise but informative representation that is easy for a
237      * person to read.
238      * It is recommended that all subclasses override this method.
239      * The string output is not necessarily stable over time or across
240      * JVM invocations.
241      * @implSpec
242      * The {@code toString} method for class {@code Object}

243      * returns a string consisting of the name of the class of which the
244      * object is an instance, the at-sign character `{@code @}', and
245      * the unsigned hexadecimal representation of the hash code of the
246      * object. In other words, this method returns a string equal to the
247      * value of:
248      * <blockquote>
249      * <pre>
250      * getClass().getName() + '@' + Integer.toHexString(hashCode())
251      * </pre></blockquote>






252      *
253      * @return  a string representation of the object.
254      */
255     public String toString() {
256         return getClass().getName() + "@" + Integer.toHexString(hashCode());
257     }
258 
259     /**
260      * Wakes up a single thread that is waiting on this object's
261      * monitor. If any threads are waiting on this object, one of them
262      * is chosen to be awakened. The choice is arbitrary and occurs at
263      * the discretion of the implementation. A thread waits on an object's
264      * monitor by calling one of the {@code wait} methods.
265      * <p>
266      * The awakened thread will not be able to proceed until the current
267      * thread relinquishes the lock on this object. The awakened thread will
268      * compete in the usual manner with any other threads that might be
269      * actively competing to synchronize on this object; for example, the
270      * awakened thread enjoys no reliable privilege or disadvantage in being
271      * the next thread to lock this object.

  1 /*
  2  * Copyright (c) 1994, 2022, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.  Oracle designates this
  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.vm.annotation.IntrinsicCandidate;
 29 import jdk.internal.access.SharedSecrets;
 30 
 31 import java.util.Objects;
 32 
 33 /**
 34  * Class {@code Object} is the root of the class hierarchy.
 35  * Every class has {@code Object} as a superclass. All objects,
 36  * including arrays, implement the methods of this class.
 37  *
 38  * @see     java.lang.Class
 39  * @since   1.0
 40  */
 41 public class Object {
 42 
 43     /**
 44      * Constructs a new object.
 45      */
 46     @IntrinsicCandidate
 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

225      *               that override the {@code clone} method can also
226      *               throw this exception to indicate that an instance cannot
227      *               be cloned.
228      * @see java.lang.Cloneable
229      */
230     @IntrinsicCandidate
231     protected native Object clone() throws CloneNotSupportedException;
232 
233     /**
234      * Returns a string representation of the object.
235      * @apiNote
236      * In general, the
237      * {@code toString} method returns a string that
238      * "textually represents" this object. The result should
239      * be a concise but informative representation that is easy for a
240      * person to read.
241      * It is recommended that all subclasses override this method.
242      * The string output is not necessarily stable over time or across
243      * JVM invocations.
244      * @implSpec
245      * If this object is an instance of an identity class, then
246      * the {@code toString} method for class {@code Object}
247      * returns a string consisting of the name of the class of which the
248      * object is an instance, the at-sign character `{@code @}', and
249      * the unsigned hexadecimal representation of the hash code of the
250      * object. In other words, this method returns a string equal to the
251      * value of:
252      * <blockquote>
253      * <pre>
254      * getClass().getName() + '@' + Integer.toHexString(hashCode())
255      * </pre></blockquote>
256      * <p>
257      * If this object is an instance of a primitive class, then
258      * the {@code toString} method returns a string which contains
259      * the name of the primitive class, and string representations of
260      * all its fields.  The precise format produced by this method
261      * is unspecified and subject to change.
262      *
263      * @return  a string representation of the object.
264      */
265     public String toString() {
266         return getClass().getName() + "@" + Integer.toHexString(hashCode());
267     }
268 
269     /**
270      * Wakes up a single thread that is waiting on this object's
271      * monitor. If any threads are waiting on this object, one of them
272      * is chosen to be awakened. The choice is arbitrary and occurs at
273      * the discretion of the implementation. A thread waits on an object's
274      * monitor by calling one of the {@code wait} methods.
275      * <p>
276      * The awakened thread will not be able to proceed until the current
277      * thread relinquishes the lock on this object. The awakened thread will
278      * compete in the usual manner with any other threads that might be
279      * actively competing to synchronize on this object; for example, the
280      * awakened thread enjoys no reliable privilege or disadvantage in being
281      * the next thread to lock this object.
< prev index next >