java.lang
Class Object

java.lang.Object

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.

Since:
JDK1.0, CLDC 1.0
Version:
a/1/08 (CLDC 1.1)
See Also:
Class

Constructor Summary
Object()
           
 
Method Summary
 boolean equals(Object aOther)
          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()
          Wake up one thread blocked on a wait().
 void notifyAll()
          Wake up all threads blocked on a wait().
 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)
          Wait until notified.
 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

Object

public Object()
Method Detail

getClass

public final Class getClass()
Returns the runtime class of an object. That Class object is the object that is locked by static synchronized methods of the represented class.

Returns:
the object of type Class that represents the runtime class of the object.

hashCode

public int hashCode()
Returns a hash code value for the object. This method is supported for the benefit of hashtables such as those provided by java.util.Hashtable.

The general contract of hashCode is:

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.)

Returns:
a hash code value for this object.
See Also:
equals(java.lang.Object), Hashtable

equals

public boolean equals(Object aOther)
Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation:

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).

Parameters:
aOther - the reference object with which to compare.
Returns:
true if this object is the same as the obj argument; false otherwise.
See Also:
Boolean.hashCode(), Hashtable

toString

public String toString()
Returns a string representation of the object. In general, the 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())
 

Returns:
a string representation of the object.

notify

public final void notify()
Wake up one thread blocked on a wait(). Must be synchronized on this object otherwise an IllegalMonitorStateException will be thrown.

If multiple threads are waiting, higher priority threads will be woken in preference, otherwise the thread that gets woken is essentially random.


notifyAll

public final void notifyAll()
Wake up all threads blocked on a wait(). Must be synchronized on this object otherwise an IllegalMonitorStateException will be thrown.


wait

public final void wait(long timeout)
                throws InterruptedException
Wait until notified. Must be synchronized on this object otherwise an IllegalMonitorStateException will be thrown. The wait can terminate if one of the following things occurs:
  1. notify() or notifyAll() is called.
  2. The calling thread is interrupted.
  3. The timeout expires.

Parameters:
timeout - maximum time in milliseconds to wait. Zero means forever.
Throws:
InterruptedException

wait

public final void wait(long timeout,
                       int nanos)
                throws InterruptedException
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.

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:

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.

Parameters:
timeout - the maximum time to wait in milliseconds.
nanos - additional time, in nanoseconds range 0-999999.
Throws:
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.

wait

public final void wait()
                throws InterruptedException
Causes current thread to wait until another thread invokes the 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.

Throws:
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.
See Also:
notify(), notifyAll()


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