Class DerbyObservable
- java.lang.Object
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- org.apache.derby.iapi.services.monitor.DerbyObservable
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- Direct Known Subclasses:
BaseContainerHandle
,RawTransaction
public class DerbyObservable extends java.lang.Object
Created to provide the Observable behavior which Derby has depended on since Java 1.2 but which as deprecated in JDK 9 build 118. A DerbyObservable is an object whose state changes are being tracked.
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Field Summary
Fields Modifier and Type Field Description private boolean
_hasChanged
private java.util.ArrayList<DerbyObserver>
_observers
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Constructor Summary
Constructors Constructor Description DerbyObservable()
No-arg constructor
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
addObserver(DerbyObserver observer)
Add another observer who wants to be told about changes to this object.int
countObservers()
Return the number of observers who are watching this object.void
deleteObserver(DerbyObserver observer)
Remove a specific observer from the list of watchers.void
notifyObservers()
This method is equivalent to notifyObservers(null);void
notifyObservers(java.lang.Object extraInfo)
If this object has changed, then notify all observers.protected void
setChanged()
When the object state changes, the object calls this method in order to flag that fact.
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Field Detail
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_hasChanged
private boolean _hasChanged
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_observers
private java.util.ArrayList<DerbyObserver> _observers
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Method Detail
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addObserver
public void addObserver(DerbyObserver observer)
Add another observer who wants to be told about changes to this object.- Parameters:
observer
- The object which wants to be notified when this object changes- Throws:
java.lang.IllegalArgumentException
- If the argument is bad (e.g., null)
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countObservers
public int countObservers()
Return the number of observers who are watching this object.- Returns:
- The number of watchers
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deleteObserver
public void deleteObserver(DerbyObserver observer)
Remove a specific observer from the list of watchers. Null is ignored.- Parameters:
observer
- The observer to remove.
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notifyObservers
public void notifyObservers()
This method is equivalent to notifyObservers(null);
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notifyObservers
public void notifyObservers(java.lang.Object extraInfo)
If this object has changed, then notify all observers. Pass them this object and the extraInfo. This object is then marked as unchanged again.- Parameters:
extraInfo
- Extra information to be passed to the observer's callback method.
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setChanged
protected void setChanged()
When the object state changes, the object calls this method in order to flag that fact. After this method has been called, then the notifyObservers() will wake up the observers which are watching this object.
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