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java.lang.Object
@TransactionType(value=NOT_SUPPORTED) public class Object
Class Object
is the root of the class hierarchy. Every class
has Object
as a superclass. All objects, including arrays,
implement the methods of this class.
Class
Constructor Summary | |
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Object()
|
Method Summary | |
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boolean |
equals(Object obj)
Indicates whether some other object is "equal to" this one. |
Class<?> |
getClass()
Returns the runtime class of an object. |
int |
hashCode()
Returns a hash code value for the object. |
void |
notify()
Wakes up a single thread that is waiting on this object's monitor. |
void |
notifyAll()
Wakes up all threads that are waiting on this object's monitor. |
String |
toString()
Returns a string representation of the object. |
void |
wait()
Causes current thread to wait until another thread invokes the notify() method or the
notifyAll() method for this object. |
void |
wait(long timeout)
Causes current thread to wait until either another thread invokes the notify() method or the
notifyAll() method for this object, or a
specified amount of time has elapsed. |
void |
wait(long timeout,
int nanos)
Causes current thread to wait until another thread invokes the notify() method or the
notifyAll() method for this object, or some
other thread interrupts the current thread, or a certain amount of real
time has elapsed. |
Constructor Detail |
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public Object()
Method Detail |
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public final Class<?> getClass()
Class
that represents the
runtime class of the object.public int hashCode()
java.util.Hashtable
.
The general contract of hashCode
is:
hashCode
method on each of the
two objects must produce the same integer result.
equals(java.lang.Object)
method, then calling the hashCode method on each of the two
objects must produce distinct integer results. However, the programmer
should be aware that producing distinct integer results for unequal
objects may improve the performance of hashtables.
As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the JavaTM programming language.)
equals(java.lang.Object)
,
Hashtable
public boolean equals(Object obj)
The equals
method implements an equivalence relation:
x
,
x.equals(x)
should return true
.
x
and y
, x.equals(y)
should return
true
if and only if y.equals(x)
returns
true
.
x
,
y
, and z
, if x.equals(y)
returns true
and y.equals(z)
returns
true
, then x.equals(z)
should return
true
.
x
and y
, multiple invocations of x.equals(y)
consistently return true
or consistently return
false
, provided no information used in
equals
comparisons on the object is modified.
x
,
x.equals(null)
should return false
.
The equals method for class Object
implements
the most discriminating possible equivalence relation on objects; that
is, for any reference values x
and y
, this
method returns true
if and only if x
and
y
refer to the same object (x==y
has the
value true
).
obj
- the reference object with which to compare.
true
if this object is the same as the obj
argument; false
otherwise.Boolean.hashCode()
,
Hashtable
public String toString()
toString
method returns a string that "textually
represents" this object. The result should be a concise but informative
representation that is easy for a person to read. It is recommended that
all subclasses override this method.
The toString
method for class Object
returns a string consisting of the name of the class of which the object
is an instance, the at-sign character `@
', and the
unsigned hexadecimal representation of the hash code of the object. In
other words, this method returns a string equal to the value of:
getClass().getName() + '@' + Integer.toHexString(hashCode())
public final void notify()
wait
methods.
The awakened thread will not be able to proceed until the current thread relinquishes the lock on this object. The awakened thread will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened thread enjoys no reliable privilege or disadvantage in being the next thread to lock this object.
This method should only be called by a thread that is the owner of this object's monitor. A thread becomes the owner of the object's monitor in one of three ways:
synchronized
statement
that synchronizes on the object.
Class,
by executing a
synchronized static method of that class.
Only one thread at a time can own an object's monitor.
IllegalMonitorStateException
- if the current thread is not the owner of this object's
monitor.notifyAll()
,
wait()
public final void notifyAll()
wait
methods.
The awakened threads will not be able to proceed until the current thread relinquishes the lock on this object. The awakened threads will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened threads enjoy no reliable privilege or disadvantage in being the next thread to lock this object.
This method should only be called by a thread that is the owner of this
object's monitor. See the notify
method for a description
of the ways in which a thread can become the owner of a monitor.
IllegalMonitorStateException
- if the current thread is not the owner of this object's
monitor.notify()
,
wait()
public final void wait(long timeout) throws InterruptedException
notify()
method or the
notifyAll()
method for this object, or a
specified amount of time has elapsed.
The current thread must own this object's monitor.
This method causes the current thread (call it T) to place itself in the wait set for this object and then to relinquish any and all synchronization claims on this object. Thread T becomes disabled for thread scheduling purposes and lies dormant until one of four things happens:
interrupts
thread T.
The thread T is then removed from the wait set for this object and re-enabled for thread scheduling. It then competes in the usual manner with other threads for the right to synchronize on the object; once it has gained control of the object, all its synchronization claims on the object are restored to the status quo ante - that is, to the situation as of the time that the wait method was invoked. Thread T then returns from the invocation of the wait method. Thus, on return from the wait method, the synchronization state of the object and of thread T is exactly as it was when the wait method was invoked.
If the current thread is interrupted
by another thread while it is waiting, then an
InterruptedException is thrown. This exception is not thrown
until the lock status of this object has been restored as described
above.
Note that the wait method, as it places the current thread into the wait set for this object, unlocks only this object; any other objects on which the current thread may be synchronized remain locked while the thread waits.
This method should only be called by a thread that is the owner of this
object's monitor. See the notify
method for a description
of the ways in which a thread can become the owner of a monitor.
timeout
- the maximum time to wait in milliseconds.
IllegalArgumentException
- if the value of timeout is negative.
IllegalMonitorStateException
- if the current thread is not the owner of the object's
monitor.
InterruptedException
- if another thread has interrupted the current thread. The
interrupted status of the current thread is
cleared when this exception is thrown.notify()
,
notifyAll()
public final void wait(long timeout, int nanos) throws InterruptedException
notify()
method or the
notifyAll()
method for this object, or some
other thread interrupts the current thread, or a certain amount of real
time has elapsed.
This method is similar to the wait
method of one argument,
but it allows finer control over the amount of time to wait for a
notification before giving up. The amount of real time, measured in
nanoseconds, is given by:
1000000 * timeout + nanos
In all other respects, this method does the same thing as the method
wait(long)
of one argument. In particular, wait(0, 0)
means the same thing as wait(0).
The current thread must own this object's monitor. The thread releases ownership of this monitor and waits until either of the following two conditions has occurred:
notify
method or the
notifyAll
method.
timeout
milliseconds
plus nanos
nanoseconds arguments, has elapsed.
The thread then waits until it can re-obtain ownership of the monitor and resumes execution
This method should only be called by a thread that is the owner of this
object's monitor. See the notify
method for a description
of the ways in which a thread can become the owner of a monitor.
timeout
- the maximum time to wait in milliseconds.nanos
- additional time, in nanoseconds range 0-999999.
IllegalArgumentException
- if the value of timeout is negative or the value of nanos
is not in the range 0-999999.
IllegalMonitorStateException
- if the current thread is not the owner of this object's
monitor.
InterruptedException
- if another thread has interrupted the current thread. The
interrupted status of the current thread is
cleared when this exception is thrown.public final void wait() throws InterruptedException
notify()
method or the
notifyAll()
method for this object. In other
word's this method behaves exactly as if it simply performs the call
wait(0).
The current thread must own this object's monitor. The thread releases
ownership of this monitor and waits until another thread notifies threads
waiting on this object's monitor to wake up either through a call to the
notify
method or the notifyAll
method. The
thread then waits until it can re-obtain ownership of the monitor and
resumes execution.
This method should only be called by a thread that is the owner of this
object's monitor. See the notify
method for a description
of the ways in which a thread can become the owner of a monitor.
IllegalMonitorStateException
- if the current thread is not the owner of the object's
monitor.
InterruptedException
- if another thread has interrupted the current thread. The
interrupted status of the current thread is
cleared when this exception is thrown.notify()
,
notifyAll()
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