AccessibleContext represents the minimum information all accessible objects return. This information includes the accessible name, description, role, and state of the object, as well as information about its parent and children. AccessibleContext also contains methods for obtaining more specific accessibility information about a component. If the component supports them, these methods will return an object that implements one or more of the following interfaces:

@beaninfo
attribute: isContainer false description: Minimal information that all accessible objects return
@version
1.43 04/02/04
@author
Peter Korn
@author
Hans Muller
@author
Willie Walker
@author
Lynn Monsanto
Constant used to indicate that the supported set of actions has changed. The old value in the PropertyChangeEvent will be an Integer representing the old number of actions supported and the new value will be an Integer representing the new number of actions supported.
Constant used to determine when the active descendant of a component has changed. The active descendant is used for objects such as list, tree, and table, which may have transient children. When the active descendant has changed, the old value of the property change event will be the Accessible representing the previous active child, and the new value will be the Accessible representing the current active child.
Constant used to determine when the accessibleText caret has changed. The old value in the PropertyChangeEvent will be an integer representing the old caret position, and the new value will be an integer representing the new/current caret position.
Constant used to determine when Accessible children are added/removed from the object. If an Accessible child is being added, the old value will be null and the new value will be the Accessible child. If an Accessible child is being removed, the old value will be the Accessible child, and the new value will be null.
PropertyChangeEvent which indicates that a change has occurred in a component's bounds. The oldValue is the old component bounds and the newValue is the new component bounds.
@since
1.5
Constant used to determine when the accessibleDescription property has changed. The old value in the PropertyChangeEvent will be the old accessibleDescription and the new value will be the new accessibleDescription.
Constant used to indicate that a hypertext element has received focus. The old value in the PropertyChangeEvent will be an Integer representing the start index in the document of the previous element that had focus and the new value will be an Integer representing the start index in the document of the current element that has focus. A value of -1 indicates that an element does not or did not have focus.
PropertyChangeEvent which indicates that a significant change has occurred to the children of a component like a tree or text. This change notifies the event listener that it needs to reacquire the state of the subcomponents. The oldValue is null and the newValue is the component whose children have become invalid.
Constant used to determine when the accessibleName property has changed. The old value in the PropertyChangeEvent will be the old accessibleName and the new value will be the new accessibleName.
Constant used to determine when the accessibleSelection has changed. The old and new values in the PropertyChangeEvent are currently reserved for future use.
Constant used to determine when the accessibleStateSet property has changed. The old value will be the old AccessibleState and the new value will be the new AccessibleState in the accessibleStateSet. For example, if a component that supports the vertical and horizontal states changes its orientation from vertical to horizontal, the old value will be AccessibleState.VERTICAL and the new value will be AccessibleState.HORIZONTAL. Please note that either value can also be null. For example, when a component changes from being enabled to disabled, the old value will be AccessibleState.ENABLED and the new value will be null.
Constant used to indicate that the table caption has changed The old value in the PropertyChangeEvent will be an Accessible representing the previous table caption and the new value will be an Accessible representing the new table caption.
Constant used to indicate that the column description has changed The old value in the PropertyChangeEvent will be null and the new value will be an Integer representing the column index.
Constant used to indicate that the column header has changed The old value in the PropertyChangeEvent will be null and the new value will be an AccessibleTableModelChange representing the header change.
Constant used to indicate that table data has changed. The old value in the PropertyChangeEvent will be null and the new value will be an AccessibleTableModelChange representing the table change.
Constant used to indicate that the row description has changed The old value in the PropertyChangeEvent will be null and the new value will be an Integer representing the row index.
Constant used to indicate that the row header has changed The old value in the PropertyChangeEvent will be null and the new value will be an AccessibleTableModelChange representing the header change.
Constant used to indicate that the table summary has changed The old value in the PropertyChangeEvent will be an Accessible representing the previous table summary and the new value will be an Accessible representing the new table summary.
PropertyChangeEvent which indicates that text attributes have changed.
For attribute insertion, the oldValue is null and the newValue is an AccessibleAttributeSequence specifying the attributes that were inserted.
For attribute deletion, the oldValue is an AccessibleAttributeSequence specifying the attributes that were deleted and the newValue is null.
For attribute replacement, the oldValue is an AccessibleAttributeSequence specifying the old attributes and the newValue is an AccessibleAttributeSequence specifying the new attributes.
PropertyChangeEvent which indicates that text has changed.
For text insertion, the oldValue is null and the newValue is an AccessibleTextSequence specifying the text that was inserted.
For text deletion, the oldValue is an AccessibleTextSequence specifying the text that was deleted and the newValue is null.
For text replacement, the oldValue is an AccessibleTextSequence specifying the old text and the newValue is an AccessibleTextSequence specifying the new text.
Constant used to determine when the accessibleValue property has changed. The old value in the PropertyChangeEvent will be a Number representing the old value and the new value will be a Number representing the new value
Constant used to determine when the visual appearance of the object has changed. The old and new values in the PropertyChangeEvent are currently reserved for future use.
Adds a PropertyChangeListener to the listener list. The listener is registered for all Accessible properties and will be called when those properties change.
Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

  • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
  • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
  • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
  • It is consistent: for any non-null reference values 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 objects is modified.
  • For any non-null reference value 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 non-null 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).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Parameters
objthe reference object with which to compare.
Return
true if this object is the same as the obj argument; false otherwise.
Support for reporting bound property changes. If oldValue and newValue are not equal and the PropertyChangeEvent listener list is not empty, then fire a PropertyChange event to each listener. In general, this is for use by the Accessible objects themselves and should not be called by an application program.
Parameters
propertyNameThe programmatic name of the property that was changed.
oldValueThe old value of the property.
newValueThe new value of the property.
Gets the AccessibleAction associated with this object that supports one or more actions.
Return
AccessibleAction if supported by object; else return null
Returns the specified Accessible child of the object. The Accessible children of an Accessible object are zero-based, so the first child of an Accessible child is at index 0, the second child is at index 1, and so on.
Parameters
izero-based index of child
Return
the Accessible child of the object
Returns the number of accessible children of the object.
Return
the number of accessible children of the object.
Gets the AccessibleComponent associated with this object that has a graphical representation.
Return
AccessibleComponent if supported by object; else return null
Gets the accessibleDescription property of this object. The accessibleDescription property of this object is a short localized phrase describing the purpose of the object. For example, in the case of a 'Cancel' button, the accessibleDescription could be 'Ignore changes and close dialog box.'
Return
the localized description of the object; null if this object does not have a description
Gets the AccessibleEditableText associated with this object presenting editable text on the display.
Return
AccessibleEditableText if supported by object; else return null
Gets the AccessibleIcons associated with an object that has one or more associated icons
Return
an array of AccessibleIcon if supported by object; otherwise return null
Gets the 0-based index of this object in its accessible parent.
Return
the 0-based index of this object in its parent; -1 if this object does not have an accessible parent.
Gets the accessibleName property of this object. The accessibleName property of an object is a localized String that designates the purpose of the object. For example, the accessibleName property of a label or button might be the text of the label or button itself. In the case of an object that doesn't display its name, the accessibleName should still be set. For example, in the case of a text field used to enter the name of a city, the accessibleName for the en_US locale could be 'city.'
Return
the localized name of the object; null if this object does not have a name
Gets the Accessible parent of this object.
Return
the Accessible parent of this object; null if this object does not have an Accessible parent
Gets the AccessibleRelationSet associated with an object
Return
an AccessibleRelationSet if supported by object; otherwise return null
Gets the role of this object. The role of the object is the generic purpose or use of the class of this object. For example, the role of a push button is AccessibleRole.PUSH_BUTTON. The roles in AccessibleRole are provided so component developers can pick from a set of predefined roles. This enables assistive technologies to provide a consistent interface to various tweaked subclasses of components (e.g., use AccessibleRole.PUSH_BUTTON for all components that act like a push button) as well as distinguish between sublasses that behave differently (e.g., AccessibleRole.CHECK_BOX for check boxes and AccessibleRole.RADIO_BUTTON for radio buttons).

Note that the AccessibleRole class is also extensible, so custom component developers can define their own AccessibleRole's if the set of predefined roles is inadequate.

Return
an instance of AccessibleRole describing the role of the object
Gets the AccessibleSelection associated with this object which allows its Accessible children to be selected.
Return
AccessibleSelection if supported by object; else return null
Gets the state set of this object. The AccessibleStateSet of an object is composed of a set of unique AccessibleStates. A change in the AccessibleStateSet of an object will cause a PropertyChangeEvent to be fired for the ACCESSIBLE_STATE_PROPERTY property.
Return
an instance of AccessibleStateSet containing the current state set of the object
Gets the AccessibleTable associated with an object
Return
an AccessibleTable if supported by object; otherwise return null
Gets the AccessibleText associated with this object presenting text on the display.
Return
AccessibleText if supported by object; else return null
Gets the AccessibleValue associated with this object that supports a Numerical value.
Return
AccessibleValue if supported by object; else return null
Returns the runtime class of an object. That Class object is the object that is locked by static synchronized methods of the represented class.
Return
The java.lang.Class object that represents the runtime class of the object. The result is of type {@code Class} where X is the erasure of the static type of the expression on which getClass is called.
Gets the locale of the component. If the component does not have a locale, then the locale of its parent is returned.
Return
this component's locale. If this component does not have a locale, the locale of its parent is returned.
Throws
IllegalComponentStateExceptionIf the Component does not have its own locale and has not yet been added to a containment hierarchy such that the locale can be determined from the containing parent.
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:

  • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
  • If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
  • It is not required that if two objects are unequal according to the 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.)

Return
a hash code value for this object.
Wakes up a single thread that is waiting on this object's monitor. If any threads are waiting on this object, one of them is chosen to be awakened. The choice is arbitrary and occurs at the discretion of the implementation. A thread waits on an object's monitor by calling one of the 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:

  • By executing a synchronized instance method of that object.
  • By executing the body of a synchronized statement that synchronizes on the object.
  • For objects of type Class, by executing a synchronized static method of that class.

Only one thread at a time can own an object's monitor.

Throws
IllegalMonitorStateExceptionif the current thread is not the owner of this object's monitor.
Wakes up all threads that are waiting on this object's monitor. A thread waits on an object's monitor by calling one of the 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.

Throws
IllegalMonitorStateExceptionif the current thread is not the owner of this object's monitor.
Removes a PropertyChangeListener from the listener list. This removes a PropertyChangeListener that was registered for all properties.
Parameters
listenerThe PropertyChangeListener to be removed
Sets the accessible description of this object. Changing the name will cause a PropertyChangeEvent to be fired for the ACCESSIBLE_DESCRIPTION_PROPERTY property.
Parameters
sthe new localized description of the object
@beaninfo
preferred: true description: Sets the accessible description for the component.
Sets the localized accessible name of this object. Changing the name will cause a PropertyChangeEvent to be fired for the ACCESSIBLE_NAME_PROPERTY property.
Parameters
sthe new localized name of the object.
@beaninfo
preferred: true description: Sets the accessible name for the component.
Sets the Accessible parent of this object. This is meant to be used only in the situations where the actual component's parent should not be treated as the component's accessible parent and is a method that should only be called by the parent of the accessible child.
Parameters
a- Accessible to be set as the parent
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())
 
Return
a string representation of the object.
Causes current thread to wait until another thread invokes the method or the method for this object. In other words, 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.

As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:

     synchronized (obj) {
         while (<condition does not hold>)
             obj.wait();
         ... // Perform action appropriate to condition
     }
 
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
IllegalMonitorStateExceptionif the current thread is not the owner of the object's monitor.
InterruptedExceptionif another thread interrupted the current thread before or while the current thread was waiting for a notification. The interrupted status of the current thread is cleared when this exception is thrown.
Causes current thread to wait until either another thread invokes the method or the 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:

  • Some other thread invokes the notify method for this object and thread T happens to be arbitrarily chosen as the thread to be awakened.
  • Some other thread invokes the notifyAll method for this object.
  • Some other thread interrupts thread T.
  • The specified amount of real time has elapsed, more or less. If timeout is zero, however, then real time is not taken into consideration and the thread simply waits until notified.
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.

A thread can also wake up without being notified, interrupted, or timing out, a so-called spurious wakeup. While this will rarely occur in practice, applications must guard against it by testing for the condition that should have caused the thread to be awakened, and continuing to wait if the condition is not satisfied. In other words, waits should always occur in loops, like this one:

     synchronized (obj) {
         while (<condition does not hold>)
             obj.wait(timeout);
         ... // Perform action appropriate to condition
     }
 
(For more information on this topic, see Section 3.2.3 in Doug Lea's "Concurrent Programming in Java (Second Edition)" (Addison-Wesley, 2000), or Item 50 in Joshua Bloch's "Effective Java Programming Language Guide" (Addison-Wesley, 2001).

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.

Parameters
timeoutthe maximum time to wait in milliseconds.
Throws
IllegalArgumentExceptionif the value of timeout is negative.
IllegalMonitorStateExceptionif the current thread is not the owner of the object's monitor.
InterruptedExceptionif another thread interrupted the current thread before or while the current thread was waiting for a notification. The interrupted status of the current thread is cleared when this exception is thrown.
Causes current thread to wait until another thread invokes the method or the 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 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:

  • 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 timeout period, specified by timeout milliseconds plus nanos nanoseconds arguments, has elapsed.

The thread then waits until it can re-obtain ownership of the monitor and resumes execution.

As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:

     synchronized (obj) {
         while (<condition does not hold>)
             obj.wait(timeout, nanos);
         ... // Perform action appropriate to condition
     }
 
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
timeoutthe maximum time to wait in milliseconds.
nanosadditional time, in nanoseconds range 0-999999.
Throws
IllegalArgumentExceptionif the value of timeout is negative or the value of nanos is not in the range 0-999999.
IllegalMonitorStateExceptionif the current thread is not the owner of this object's monitor.
InterruptedExceptionif another thread interrupted the current thread before or while the current thread was waiting for a notification. The interrupted status of the current thread is cleared when this exception is thrown.