Object.java: Added javadocs all over (merged from GNU classpath).
2004-11-16 Michael Koch <konqueror@gmx.de> * java/lang/Object.java: Added javadocs all over (merged from GNU classpath). From-SVN: r90766
This commit is contained in:
Michael Koch
Michael Koch
parent
fd9065b2ef
commit
0b43493272
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@ -1,3 +1,8 @@
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2004-11-16 Michael Koch <konqueror@gmx.de>
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* java/lang/Object.java: Added javadocs all over (merged from GNU
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classpath).
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2004-11-16 Andreas Tobler <a.tobler@schweiz.ch>
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* java/security/Security.java (Security): Silence the warning about no
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@ -39,11 +39,6 @@ exception statement from your version. */
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package java.lang;
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/**
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* @author Tom Tromey <tromey@cygnus.com>
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* @date September 30, 1998
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*/
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/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
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* "The Java Language Specification", ISBN 0-201-63451-1
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* plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
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@ -51,49 +46,465 @@ package java.lang;
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* Status: Complete to version 1.1
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*/
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/**
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* Object is the ultimate superclass of every class
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* (excepting interfaces). When you define a class that
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* does not extend any other class, it implicitly extends
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* java.lang.Object. Also, an anonymous class based on
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* an interface will extend Object.
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*
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* <p>It provides general-purpose methods that every single
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* Object, regardless of race, sex or creed, implements.
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* All of the public methods may be invoked on arrays or
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* interfaces. The protected methods <code>clone</code>
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* and <code>finalize</code> are not accessible on arrays
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* or interfaces, but all array types have a public version
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* of <code>clone</code> which is accessible.
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*
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* @author John Keiser
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* @author Eric Blake (ebb9@email.byu.edu)
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* @author Tom Tromey (tromey@cygnus.com)
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*/
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public class Object
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{
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/**
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* Called on an object by the Virtual Machine at most once,
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* at some point after the Object is determined unreachable
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* but before it is destroyed. You would think that this
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* means it eventually is called on every Object, but this is
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* not necessarily the case. If execution terminates
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* abnormally, garbage collection does not always happen.
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* Thus you cannot rely on this method to always work.
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* For finer control over garbage collection, use references
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* from the {@link java.lang.ref} package.
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*
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* <p>Virtual Machines are free to not call this method if
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* they can determine that it does nothing important; for
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* example, if your class extends Object and overrides
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* finalize to do simply <code>super.finalize()</code>.
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*
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* <p>finalize() will be called by a {@link Thread} that has no
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* locks on any Objects, and may be called concurrently.
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* There are no guarantees on the order in which multiple
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* objects are finalized. This means that finalize() is
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* usually unsuited for performing actions that must be
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* thread-safe, and that your implementation must be
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* use defensive programming if it is to always work.
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*
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* <p>If an Exception is thrown from finalize() during garbage
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* collection, it will be patently ignored and the Object will
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* still be destroyed.
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*
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* <p>It is allowed, although not typical, for user code to call
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* finalize() directly. User invocation does not affect whether
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* automatic invocation will occur. It is also permitted,
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* although not recommended, for a finalize() method to "revive"
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* an object by making it reachable from normal code again.
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*
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* <p>Unlike constructors, finalize() does not get called
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* for an object's superclass unless the implementation
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* specifically calls <code>super.finalize()</code>.
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*
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* <p>The default implementation does nothing.
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*
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* @throws Throwable permits a subclass to throw anything in an
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* overridden version; but the default throws nothing
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* @see System#gc()
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* @see System#runFinalizersOnExit(boolean)
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* @see java.lang.ref
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*/
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// This must come first. See _JvObjectPrefix in Object.h.
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protected void finalize () throws Throwable
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{
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}
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public final native Class getClass ();
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public native int hashCode ();
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public final native void notify ();
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public final native void notifyAll ();
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public final native void wait (long timeout, int nanos)
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/**
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* Returns the runtime {@link Class} of this Object.
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*
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* <p>The class object can also be obtained without a runtime
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* instance by using the class literal, as in:
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* <code>Foo.class</code>. Notice that the class literal
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* also works on primitive types, making it useful for
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* reflection purposes.
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*
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* @return the class of this Object
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*/
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public final native Class getClass();
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/**
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* Get a value that represents this Object, as uniquely as
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* possible within the confines of an int.
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*
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* <p>There are some requirements on this method which
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* subclasses must follow:<br>
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*
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* <ul>
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* <li>Semantic equality implies identical hashcodes. In other
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* words, if <code>a.equals(b)</code> is true, then
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* <code>a.hashCode() == b.hashCode()</code> must be as well.
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* However, the reverse is not necessarily true, and two
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* objects may have the same hashcode without being equal.</li>
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* <li>It must be consistent. Whichever value o.hashCode()
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* returns on the first invocation must be the value
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* returned on all later invocations as long as the object
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* exists. Notice, however, that the result of hashCode may
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* change between separate executions of a Virtual Machine,
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* because it is not invoked on the same object.</li>
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* </ul>
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*
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* <p>Notice that since <code>hashCode</code> is used in
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* {@link java.util.Hashtable} and other hashing classes,
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* a poor implementation will degrade the performance of hashing
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* (so don't blindly implement it as returning a constant!). Also,
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* if calculating the hash is time-consuming, a class may consider
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* caching the results.
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*
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* <p>The default implementation returns
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* <code>System.identityHashCode(this)</code>
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*
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* @return the hash code for this Object
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* @see #equals(Object)
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* @see System#identityHashCode(Object)
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*/
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public native int hashCode();
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/**
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* Wakes up one of the {@link Thread}s that has called
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* <code>wait</code> on this Object. Only the owner
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* of a lock on this Object may call this method. This lock
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* is obtained by a <code>synchronized</code> method or statement.
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*
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* <p>The Thread to wake up is chosen arbitrarily. The
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* awakened thread is not guaranteed to be the next thread
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* to actually obtain the lock on this object.
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*
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* <p>This thread still holds a lock on the object, so it is
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* typical to release the lock by exiting the synchronized
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* code, calling wait(), or calling {@link Thread#sleep()}, so
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* that the newly awakened thread can actually resume. The
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* awakened thread will most likely be awakened with an
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* {@link InterruptedException}, but that is not guaranteed.
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*
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* @throws IllegalMonitorStateException if this Thread
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* does not own the lock on the Object
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* @see #notifyAll()
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* @see #wait()
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* @see #wait(long)
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* @see #wait(long, int)
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* @see Thread
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*/
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public final native void notify();
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/**
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* Wakes up all of the {@link Thread}s that have called
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* <code>wait</code> on this Object. Only the owner
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* of a lock on this Object may call this method. This lock
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* is obtained by a <code>synchronized</code> method or statement.
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*
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* <p>There are no guarantees as to which thread will next
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* obtain the lock on the object.
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*
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* <p>This thread still holds a lock on the object, so it is
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* typical to release the lock by exiting the synchronized
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* code, calling wait(), or calling {@link Thread#sleep()}, so
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* that one of the newly awakened threads can actually resume.
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* The resuming thread will most likely be awakened with an
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* {@link InterruptedException}, but that is not guaranteed.
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*
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* @throws IllegalMonitorStateException if this Thread
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* does not own the lock on the Object
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* @see #notify()
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* @see #wait()
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* @see #wait(long)
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* @see #wait(long, int)
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* @see Thread
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*/
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public final native void notifyAll();
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/**
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* Waits a specified amount of time (or indefinitely if
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* the time specified is 0) for someone to call notify()
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* or notifyAll() on this Object, waking up this Thread.
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*
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* <p>The Thread that calls wait must have a lock on this Object,
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* obtained by a <code>synchronized</code> method or statement.
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* After calling wait, the thread loses the lock on this
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* object until the method completes (abruptly or normally),
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* at which time it regains the lock. All locks held on
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* other objects remain in force, even though the thread is
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* inactive. Therefore, caution must be used to avoid deadlock.
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*
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* <p>Usually, this call will complete normally if the time
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* expires, or abruptly with {@link InterruptedException}
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* if another thread called notify, but neither result
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* is guaranteed.
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*
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* <p>The waiting period is nowhere near as precise as
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* nanoseconds; considering that even wait(int) is inaccurate,
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* how much can you expect? But on supporting
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* implementations, this offers somewhat more granularity
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* than milliseconds.
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*
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* @param ms the number of milliseconds to wait (1,000
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* milliseconds = 1 second)
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* @param ns the number of nanoseconds to wait over and
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* above ms (1,000,000 nanoseconds = 1 millisecond)
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* @throws IllegalArgumentException if ms < 0 or ns is not
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* in the range 0 to 999,999
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* @throws IllegalMonitorStateException if this Thread
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* does not own a lock on this Object
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* @throws InterruptedException if some other Thread
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* interrupts this Thread
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* @see #notify()
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* @see #notifyAll()
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* @see #wait()
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* @see #wait(long)
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* @see Thread
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*/
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public final native void wait(long timeout, int nanos)
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throws InterruptedException;
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public boolean equals (Object obj)
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/**
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* Determine whether this Object is semantically equal
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* to another Object.
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*
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* <p>There are some fairly strict requirements on this
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* method which subclasses must follow:<br>
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* <ul>
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* <li>It must be transitive. If <code>a.equals(b)</code> and
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* <code>b.equals(c)</code>, then <code>a.equals(c)</code>
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* must be true as well.</li>
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* <li>It must be symmetric. <code>a.equals(b)</code> and
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* <code>b.equals(a)</code> must have the same value.</li>
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* <li>It must be reflexive. <code>a.equals(a)</code> must
|
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* always be true.</li>
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* <li>It must be consistent. Whichever value a.equals(b)
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* returns on the first invocation must be the value
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* returned on all later invocations.</li>
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* <li><code>a.equals(null)</code> must be false.</li>
|
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* <li>It must be consistent with hashCode(). That is,
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* <code>a.equals(b)</code> must imply
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* <code>a.hashCode() == b.hashCode()</code>.
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* The reverse is not true; two objects that are not
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* equal may have the same hashcode, but that has
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* the potential to harm hashing performance.</li>
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* </ul>
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*
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* <p>This is typically overridden to throw a {@link ClassCastException}
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* if the argument is not comparable to the class performing
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* the comparison, but that is not a requirement. It is legal
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* for <code>a.equals(b)</code> to be true even though
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* <code>a.getClass() != b.getClass()</code>. Also, it
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* is typical to never cause a {@link NullPointerException}.
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*
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* <p>In general, the Collections API ({@link java.util}) use the
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* <code>equals</code> method rather than the <code>==</code>
|
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* operator to compare objects. However, {@link java.util.IdentityHashMap}
|
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* is an exception to this rule, for its own good reasons.
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*
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* <p>The default implementation returns <code>this == o</code>.
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*
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* @param obj the Object to compare to
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* @return whether this Object is semantically equal to another
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* @see #hashCode()
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*/
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public boolean equals(Object obj)
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{
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return this == obj;
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}
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public Object ()
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/**
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* The basic constructor. Object is special, because it has no
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* superclass, so there is no call to super().
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*
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* @throws OutOfMemoryError Technically, this constructor never
|
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* throws an OutOfMemoryError, because the memory has
|
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* already been allocated by this point. But as all
|
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* instance creation expressions eventually trace back
|
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* to this constructor, and creating an object allocates
|
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* memory, we list that possibility here.
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*/
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public Object()
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{
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}
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public String toString ()
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/**
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* Convert this Object to a human-readable String.
|
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* There are no limits placed on how long this String
|
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* should be or what it should contain. We suggest you
|
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* make it as intuitive as possible to be able to place
|
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* it into {@link java.io.PrintStream#println() System.out.println()}
|
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* and such.
|
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*
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* <p>It is typical, but not required, to ensure that this method
|
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* never completes abruptly with a {@link RuntimeException}.
|
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*
|
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* <p>This method will be called when performing string
|
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* concatenation with this object. If the result is
|
||||
* <code>null</code>, string concatenation will instead
|
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* use <code>"null"</code>.
|
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*
|
||||
* <p>The default implementation returns
|
||||
* <code>getClass().getName() + "@" +
|
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* Integer.toHexString(hashCode())</code>.
|
||||
*
|
||||
* @return the String representing this Object, which may be null
|
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* @throws OutOfMemoryError The default implementation creates a new
|
||||
* String object, therefore it must allocate memory
|
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* @see #getClass()
|
||||
* @see #hashCode()
|
||||
* @see Class#getName()
|
||||
* @see Integer#toHexString(int)
|
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*/
|
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public String toString()
|
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{
|
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return getClass().getName() + '@' + Integer.toHexString(hashCode());
|
||||
}
|
||||
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||||
public final void wait () throws InterruptedException
|
||||
/**
|
||||
* Waits indefinitely for notify() or notifyAll() to be
|
||||
* called on the Object in question. Implementation is
|
||||
* identical to wait(0).
|
||||
*
|
||||
* <p>The Thread that calls wait must have a lock on this Object,
|
||||
* obtained by a <code>synchronized</code> method or statement.
|
||||
* After calling wait, the thread loses the lock on this
|
||||
* object until the method completes (abruptly or normally),
|
||||
* at which time it regains the lock. All locks held on
|
||||
* other objects remain in force, even though the thread is
|
||||
* inactive. Therefore, caution must be used to avoid deadlock.
|
||||
*
|
||||
* <p>While it is typical that this method will complete abruptly
|
||||
* with an {@link InterruptedException}, it is not guaranteed. So,
|
||||
* it is typical to call wait inside an infinite loop:<br>
|
||||
*
|
||||
* <pre>
|
||||
* try
|
||||
* {
|
||||
* while (true)
|
||||
* lock.wait();
|
||||
* }
|
||||
* catch (InterruptedException e)
|
||||
* {
|
||||
* }
|
||||
* </pre>
|
||||
*
|
||||
* @throws IllegalMonitorStateException if this Thread
|
||||
* does not own a lock on this Object
|
||||
* @throws InterruptedException if some other Thread
|
||||
* interrupts this Thread
|
||||
* @see #notify()
|
||||
* @see #notifyAll()
|
||||
* @see #wait(long)
|
||||
* @see #wait(long, int)
|
||||
* @see Thread
|
||||
*/
|
||||
public final void wait() throws InterruptedException
|
||||
{
|
||||
wait (0, 0);
|
||||
wait(0, 0);
|
||||
}
|
||||
|
||||
public final void wait (long timeout) throws InterruptedException
|
||||
/**
|
||||
* Waits a specified amount of time (or indefinitely if
|
||||
* the time specified is 0) for someone to call notify()
|
||||
* or notifyAll() on this Object, waking up this Thread.
|
||||
*
|
||||
* <p>The Thread that calls wait must have a lock on this Object,
|
||||
* obtained by a <code>synchronized</code> method or statement.
|
||||
* After calling wait, the thread loses the lock on this
|
||||
* object until the method completes (abruptly or normally),
|
||||
* at which time it regains the lock. All locks held on
|
||||
* other objects remain in force, even though the thread is
|
||||
* inactive. Therefore, caution must be used to avoid deadlock.
|
||||
*
|
||||
* <p>Usually, this call will complete normally if the time
|
||||
* expires, or abruptly with {@link InterruptedException}
|
||||
* if another thread called notify, but neither result
|
||||
* is guaranteed.
|
||||
*
|
||||
* <p>The waiting period is only *roughly* the amount of time
|
||||
* you requested. It cannot be exact because of the overhead
|
||||
* of the call itself. Most Virtual Machiness treat the
|
||||
* argument as a lower limit on the time spent waiting, but
|
||||
* even that is not guaranteed. Besides, some other thread
|
||||
* may hold the lock on the object when the time expires, so
|
||||
* the current thread may still have to wait to reobtain the
|
||||
* lock.
|
||||
*
|
||||
* @param timeout the minimum number of milliseconds to wait (1000
|
||||
* milliseconds = 1 second), or 0 for an indefinite wait
|
||||
* @throws IllegalArgumentException if ms < 0
|
||||
* @throws IllegalMonitorStateException if this Thread
|
||||
* does not own a lock on this Object
|
||||
* @throws InterruptedException if some other Thread
|
||||
* interrupts this Thread
|
||||
* @see #notify()
|
||||
* @see #notifyAll()
|
||||
* @see #wait()
|
||||
* @see #wait(long, int)
|
||||
* @see Thread
|
||||
*/
|
||||
public final void wait(long timeout) throws InterruptedException
|
||||
{
|
||||
wait (timeout, 0);
|
||||
wait(timeout, 0);
|
||||
}
|
||||
|
||||
protected native Object clone () throws CloneNotSupportedException;
|
||||
/**
|
||||
* This method may be called to create a new copy of the
|
||||
* Object. The typical behavior is as follows:<br>
|
||||
* <ul>
|
||||
* <li><code>o == o.clone()</code> is false</li>
|
||||
* <li><code>o.getClass() == o.clone().getClass()</code>
|
||||
* is true</li>
|
||||
* <li><code>o.equals(o)</code> is true</li>
|
||||
* </ul>
|
||||
*
|
||||
* <p>However, these are not strict requirements, and may
|
||||
* be violated if necessary. Of the three requirements, the
|
||||
* last is the most commonly violated, particularly if the
|
||||
* subclass does not override {@link #equals(Object)}.
|
||||
*
|
||||
* <p>If the Object you call clone() on does not implement
|
||||
* {@link Cloneable} (which is a placeholder interface), then
|
||||
* a CloneNotSupportedException is thrown. Notice that
|
||||
* Object does not implement Cloneable; this method exists
|
||||
* as a convenience for subclasses that do.
|
||||
*
|
||||
* <p>Object's implementation of clone allocates space for the
|
||||
* new Object using the correct class, without calling any
|
||||
* constructors, and then fills in all of the new field values
|
||||
* with the old field values. Thus, it is a shallow copy.
|
||||
* However, subclasses are permitted to make a deep copy.
|
||||
*
|
||||
* <p>All array types implement Cloneable, and override
|
||||
* this method as follows (it should never fail):<br>
|
||||
* <pre>
|
||||
* public Object clone()
|
||||
* {
|
||||
* try
|
||||
* {
|
||||
* super.clone();
|
||||
* }
|
||||
* catch (CloneNotSupportedException e)
|
||||
* {
|
||||
* throw new InternalError(e.getMessage());
|
||||
* }
|
||||
* }
|
||||
* </pre>
|
||||
*
|
||||
* @return a copy of the Object
|
||||
* @throws CloneNotSupportedException If this Object does not
|
||||
* implement Cloneable
|
||||
* @throws OutOfMemoryError Since cloning involves memory allocation,
|
||||
* even though it may bypass constructors, you might run
|
||||
* out of memory
|
||||
* @see Cloneable
|
||||
*/
|
||||
protected native Object clone() throws CloneNotSupportedException;
|
||||
|
||||
// This initializes the sync_info member. It is here for
|
||||
// completeness (some day we'll be able to auto-generate Object.h).
|
||||
private final native void sync_init ();
|
||||
private final native void sync_init();
|
||||
|
||||
// Note that we don't mention the sync_info field here. If we do,
|
||||
// jc1 will not work correctly.
|
||||
|
|
|
|||
Loading…
Reference in New Issue