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org.ematgine.utils.concurrent
Class FutureResult  

java.lang.Object
  org.ematgine.utils.concurrent.FutureResult

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public class FutureResult

extends java.lang.Object

A class maintaining a single reference variable serving as the result of an operation. The result cannot be accessed until it has been set.

Sample Usage

 class ImageRenderer { Image render(byte[] raw); }
 class App {
   Executor executor = ...
   ImageRenderer renderer = ...
   void display(byte[] rawimage) {
     try {
       FutureResult futureImage = new FutureResult();
       Runnable command = futureImage.setter(new Callable() {
          public Object call() { return renderer.render(rawImage); }
       });
       executor.execute(command);
       drawBorders();             // do other things while executing
       drawCaption();
       drawImage((Image)(futureImage.get())); // use future
     }
     catch (InterruptedException ex) { return; }
     catch (InvocationTargetException ex) { cleanup(); return; }
   }
 }
 

[ Introduction to this package. ]

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Field Summary
protected  java.lang.reflect.InvocationTargetException	exception_           the exception encountered by operation producing result
protected  boolean	ready_           Status -- true after first set
protected  java.lang.Object	value_           The result of the operation

 

Constructor Summary

FutureResult()           Create an initially unset FutureResult

 

Method Summary
void	clear()           Clear the value and exception and set to not-ready, allowing this FutureResult to be reused.
protected  java.lang.Object	doGet()           internal utility: either get the value or throw the exception
java.lang.Object	get()           Access the reference, waiting if necessary until it is ready.
java.lang.reflect.InvocationTargetException	getException()           Get the exception, or null if there isn't one (yet).
boolean	isReady()           Return whether the reference or exception have been set.
java.lang.Object	peek()           Access the reference, even if not ready
void	set(java.lang.Object newValue)           Set the reference, and signal that it is ready.
void	setException(java.lang.Throwable ex)           Set the exception field, also setting ready status.
java.lang.Runnable	setter(Callable function)           Return a Runnable object that, when run, will set the result value.
java.lang.Object	timedGet(long msecs)           Wait at most msecs to access the reference.

 

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Field Detail

value_

protected java.lang.Object value_

The result of the operation

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ready_

protected boolean ready_

Status -- true after first set

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exception_

protected java.lang.reflect.InvocationTargetException exception_

the exception encountered by operation producing result

Constructor Detail

FutureResult

public FutureResult()

Create an initially unset FutureResult

Method Detail

setter

public java.lang.Runnable setter(Callable function)

Return a Runnable object that, when run, will set the result value.

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doGet

protected java.lang.Object doGet()
                          throws java.lang.reflect.InvocationTargetException

internal utility: either get the value or throw the exception

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get

public java.lang.Object get()
                     throws java.lang.InterruptedException,
                            java.lang.reflect.InvocationTargetException

Access the reference, waiting if necessary until it is ready.

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timedGet

public java.lang.Object timedGet(long msecs)
                          throws TimeoutException,
                                 java.lang.InterruptedException,
                                 java.lang.reflect.InvocationTargetException

Wait at most msecs to access the reference.

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set

public void set(java.lang.Object newValue)

Set the reference, and signal that it is ready. It is not considered an error to set the value more than once, but it is not something you would normally want to do.

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setException

public void setException(java.lang.Throwable ex)

Set the exception field, also setting ready status.

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getException

public java.lang.reflect.InvocationTargetException getException()

Get the exception, or null if there isn't one (yet). This does not wait until the future is ready, so should ordinarily only be called if you know it is.

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isReady

public boolean isReady()

Return whether the reference or exception have been set.

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peek

public java.lang.Object peek()

Access the reference, even if not ready

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clear

public void clear()

Clear the value and exception and set to not-ready, allowing this FutureResult to be reused. This is not particularly recommended and must be done only when you know that no other object is depending on the properties of this FutureResult.

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> ematgine >> utils >> [ concurrent overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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