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 2004-11-16 21:37:29 +00:00 committed by Michael Koch
parent fd9065b2ef
commit 0b43493272
2 changed files with 435 additions and 19 deletions

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@ -1,3 +1,8 @@
2004-11-16 Michael Koch <konqueror@gmx.de>
* java/lang/Object.java: Added javadocs all over (merged from GNU
classpath).
2004-11-16 Andreas Tobler <a.tobler@schweiz.ch> 2004-11-16 Andreas Tobler <a.tobler@schweiz.ch>
* java/security/Security.java (Security): Silence the warning about no * java/security/Security.java (Security): Silence the warning about no

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@ -39,11 +39,6 @@ exception statement from your version. */
package java.lang; package java.lang;
/**
* @author Tom Tromey <tromey@cygnus.com>
* @date September 30, 1998
*/
/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3 /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
* "The Java Language Specification", ISBN 0-201-63451-1 * "The Java Language Specification", ISBN 0-201-63451-1
* plus online API docs for JDK 1.2 beta from http://www.javasoft.com. * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
@ -51,44 +46,460 @@ package java.lang;
* Status: Complete to version 1.1 * Status: Complete to version 1.1
*/ */
/**
* Object is the ultimate superclass of every class
* (excepting interfaces). When you define a class that
* does not extend any other class, it implicitly extends
* java.lang.Object. Also, an anonymous class based on
* an interface will extend Object.
*
* <p>It provides general-purpose methods that every single
* Object, regardless of race, sex or creed, implements.
* All of the public methods may be invoked on arrays or
* interfaces. The protected methods <code>clone</code>
* and <code>finalize</code> are not accessible on arrays
* or interfaces, but all array types have a public version
* of <code>clone</code> which is accessible.
*
* @author John Keiser
* @author Eric Blake (ebb9@email.byu.edu)
* @author Tom Tromey (tromey@cygnus.com)
*/
public class Object public class Object
{ {
/**
* Called on an object by the Virtual Machine at most once,
* at some point after the Object is determined unreachable
* but before it is destroyed. You would think that this
* means it eventually is called on every Object, but this is
* not necessarily the case. If execution terminates
* abnormally, garbage collection does not always happen.
* Thus you cannot rely on this method to always work.
* For finer control over garbage collection, use references
* from the {@link java.lang.ref} package.
*
* <p>Virtual Machines are free to not call this method if
* they can determine that it does nothing important; for
* example, if your class extends Object and overrides
* finalize to do simply <code>super.finalize()</code>.
*
* <p>finalize() will be called by a {@link Thread} that has no
* locks on any Objects, and may be called concurrently.
* There are no guarantees on the order in which multiple
* objects are finalized. This means that finalize() is
* usually unsuited for performing actions that must be
* thread-safe, and that your implementation must be
* use defensive programming if it is to always work.
*
* <p>If an Exception is thrown from finalize() during garbage
* collection, it will be patently ignored and the Object will
* still be destroyed.
*
* <p>It is allowed, although not typical, for user code to call
* finalize() directly. User invocation does not affect whether
* automatic invocation will occur. It is also permitted,
* although not recommended, for a finalize() method to "revive"
* an object by making it reachable from normal code again.
*
* <p>Unlike constructors, finalize() does not get called
* for an object's superclass unless the implementation
* specifically calls <code>super.finalize()</code>.
*
* <p>The default implementation does nothing.
*
* @throws Throwable permits a subclass to throw anything in an
* overridden version; but the default throws nothing
* @see System#gc()
* @see System#runFinalizersOnExit(boolean)
* @see java.lang.ref
*/
// This must come first. See _JvObjectPrefix in Object.h. // This must come first. See _JvObjectPrefix in Object.h.
protected void finalize () throws Throwable protected void finalize () throws Throwable
{ {
} }
/**
* Returns the runtime {@link Class} of this Object.
*
* <p>The class object can also be obtained without a runtime
* instance by using the class literal, as in:
* <code>Foo.class</code>. Notice that the class literal
* also works on primitive types, making it useful for
* reflection purposes.
*
* @return the class of this Object
*/
public final native Class getClass(); public final native Class getClass();
/**
* Get a value that represents this Object, as uniquely as
* possible within the confines of an int.
*
* <p>There are some requirements on this method which
* subclasses must follow:<br>
*
* <ul>
* <li>Semantic equality implies identical hashcodes. In other
* words, if <code>a.equals(b)</code> is true, then
* <code>a.hashCode() == b.hashCode()</code> must be as well.
* However, the reverse is not necessarily true, and two
* objects may have the same hashcode without being equal.</li>
* <li>It must be consistent. Whichever value o.hashCode()
* returns on the first invocation must be the value
* returned on all later invocations as long as the object
* exists. Notice, however, that the result of hashCode may
* change between separate executions of a Virtual Machine,
* because it is not invoked on the same object.</li>
* </ul>
*
* <p>Notice that since <code>hashCode</code> is used in
* {@link java.util.Hashtable} and other hashing classes,
* a poor implementation will degrade the performance of hashing
* (so don't blindly implement it as returning a constant!). Also,
* if calculating the hash is time-consuming, a class may consider
* caching the results.
*
* <p>The default implementation returns
* <code>System.identityHashCode(this)</code>
*
* @return the hash code for this Object
* @see #equals(Object)
* @see System#identityHashCode(Object)
*/
public native int hashCode(); public native int hashCode();
/**
* Wakes up one of the {@link Thread}s that has called
* <code>wait</code> on this Object. Only the owner
* of a lock on this Object may call this method. This lock
* is obtained by a <code>synchronized</code> method or statement.
*
* <p>The Thread to wake up is chosen arbitrarily. The
* awakened thread is not guaranteed to be the next thread
* to actually obtain the lock on this object.
*
* <p>This thread still holds a lock on the object, so it is
* typical to release the lock by exiting the synchronized
* code, calling wait(), or calling {@link Thread#sleep()}, so
* that the newly awakened thread can actually resume. The
* awakened thread will most likely be awakened with an
* {@link InterruptedException}, but that is not guaranteed.
*
* @throws IllegalMonitorStateException if this Thread
* does not own the lock on the Object
* @see #notifyAll()
* @see #wait()
* @see #wait(long)
* @see #wait(long, int)
* @see Thread
*/
public final native void notify(); public final native void notify();
/**
* Wakes up all of the {@link Thread}s that have called
* <code>wait</code> on this Object. Only the owner
* of a lock on this Object may call this method. This lock
* is obtained by a <code>synchronized</code> method or statement.
*
* <p>There are no guarantees as to which thread will next
* obtain the lock on the object.
*
* <p>This thread still holds a lock on the object, so it is
* typical to release the lock by exiting the synchronized
* code, calling wait(), or calling {@link Thread#sleep()}, so
* that one of the newly awakened threads can actually resume.
* The resuming thread will most likely be awakened with an
* {@link InterruptedException}, but that is not guaranteed.
*
* @throws IllegalMonitorStateException if this Thread
* does not own the lock on the Object
* @see #notify()
* @see #wait()
* @see #wait(long)
* @see #wait(long, int)
* @see Thread
*/
public final native void notifyAll(); public final native void notifyAll();
/**
* 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 nowhere near as precise as
* nanoseconds; considering that even wait(int) is inaccurate,
* how much can you expect? But on supporting
* implementations, this offers somewhat more granularity
* than milliseconds.
*
* @param ms the number of milliseconds to wait (1,000
* milliseconds = 1 second)
* @param ns the number of nanoseconds to wait over and
* above ms (1,000,000 nanoseconds = 1 millisecond)
* @throws IllegalArgumentException if ms &lt; 0 or ns is not
* in the range 0 to 999,999
* @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)
* @see Thread
*/
public final native void wait(long timeout, int nanos) public final native void wait(long timeout, int nanos)
throws InterruptedException; throws InterruptedException;
/**
* Determine whether this Object is semantically equal
* to another Object.
*
* <p>There are some fairly strict requirements on this
* method which subclasses must follow:<br>
* <ul>
* <li>It must be transitive. If <code>a.equals(b)</code> and
* <code>b.equals(c)</code>, then <code>a.equals(c)</code>
* must be true as well.</li>
* <li>It must be symmetric. <code>a.equals(b)</code> and
* <code>b.equals(a)</code> must have the same value.</li>
* <li>It must be reflexive. <code>a.equals(a)</code> must
* always be true.</li>
* <li>It must be consistent. Whichever value a.equals(b)
* returns on the first invocation must be the value
* returned on all later invocations.</li>
* <li><code>a.equals(null)</code> must be false.</li>
* <li>It must be consistent with hashCode(). That is,
* <code>a.equals(b)</code> must imply
* <code>a.hashCode() == b.hashCode()</code>.
* The reverse is not true; two objects that are not
* equal may have the same hashcode, but that has
* the potential to harm hashing performance.</li>
* </ul>
*
* <p>This is typically overridden to throw a {@link ClassCastException}
* if the argument is not comparable to the class performing
* the comparison, but that is not a requirement. It is legal
* for <code>a.equals(b)</code> to be true even though
* <code>a.getClass() != b.getClass()</code>. Also, it
* is typical to never cause a {@link NullPointerException}.
*
* <p>In general, the Collections API ({@link java.util}) use the
* <code>equals</code> method rather than the <code>==</code>
* operator to compare objects. However, {@link java.util.IdentityHashMap}
* is an exception to this rule, for its own good reasons.
*
* <p>The default implementation returns <code>this == o</code>.
*
* @param obj the Object to compare to
* @return whether this Object is semantically equal to another
* @see #hashCode()
*/
public boolean equals(Object obj) public boolean equals(Object obj)
{ {
return this == obj; return this == obj;
} }
/**
* The basic constructor. Object is special, because it has no
* superclass, so there is no call to super().
*
* @throws OutOfMemoryError Technically, this constructor never
* throws an OutOfMemoryError, because the memory has
* already been allocated by this point. But as all
* instance creation expressions eventually trace back
* to this constructor, and creating an object allocates
* memory, we list that possibility here.
*/
public Object() public Object()
{ {
} }
/**
* Convert this Object to a human-readable String.
* There are no limits placed on how long this String
* should be or what it should contain. We suggest you
* make it as intuitive as possible to be able to place
* it into {@link java.io.PrintStream#println() System.out.println()}
* and such.
*
* <p>It is typical, but not required, to ensure that this method
* never completes abruptly with a {@link RuntimeException}.
*
* <p>This method will be called when performing string
* concatenation with this object. If the result is
* <code>null</code>, string concatenation will instead
* use <code>"null"</code>.
*
* <p>The default implementation returns
* <code>getClass().getName() + "@" +
* Integer.toHexString(hashCode())</code>.
*
* @return the String representing this Object, which may be null
* @throws OutOfMemoryError The default implementation creates a new
* String object, therefore it must allocate memory
* @see #getClass()
* @see #hashCode()
* @see Class#getName()
* @see Integer#toHexString(int)
*/
public String toString() public String toString()
{ {
return getClass().getName() + '@' + Integer.toHexString(hashCode()); return getClass().getName() + '@' + Integer.toHexString(hashCode());
} }
/**
* 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 public final void wait() throws InterruptedException
{ {
wait(0, 0); wait(0, 0);
} }
/**
* 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 &lt; 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 public final void wait(long timeout) throws InterruptedException
{ {
wait(timeout, 0); wait(timeout, 0);
} }
/**
* 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; protected native Object clone() throws CloneNotSupportedException;
// This initializes the sync_info member. It is here for // This initializes the sync_info member. It is here for