Package org.logicalcobwebs.concurrent
Class FutureResult
- java.lang.Object
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- org.logicalcobwebs.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; } } }
- See Also:
Executor
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Field Summary
Fields Modifier and Type Field Description protected java.lang.reflect.InvocationTargetException
exception_
the exception encountered by operation producing resultprotected boolean
ready_
Status -- true after first setprotected java.lang.Object
value_
The result of the operation
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Constructor Summary
Constructors Constructor Description FutureResult()
Create an initially unset FutureResult
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description 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 exceptionjava.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 readyvoid
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.
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Method Detail
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setter
public java.lang.Runnable setter(Callable function)
Return a Runnable object that, when run, will set the result value.- Parameters:
function
- - a Callable object whose result will be held by this FutureResult.- Returns:
- A Runnable object that, when run, will call the function and (eventually) set the result.
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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- Throws:
java.lang.reflect.InvocationTargetException
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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.- Returns:
- current value
- Throws:
java.lang.InterruptedException
- if current thread has been interruptedjava.lang.reflect.InvocationTargetException
- if the operation producing the value encountered an exception.
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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.- Returns:
- current value
- Throws:
TimeoutException
- if not ready after msecsjava.lang.InterruptedException
- if current thread has been interruptedjava.lang.reflect.InvocationTargetException
- if the operation producing the value encountered an exception.
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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.- Parameters:
newValue
- The value that will be returned by a subsequent get();
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setException
public void setException(java.lang.Throwable ex)
Set the exception field, also setting ready status.- Parameters:
ex
- The exception. It will be reported out wrapped within an InvocationTargetException
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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.- Returns:
- the exception encountered by the operation setting the future, wrapped in an InvocationTargetException
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isReady
public boolean isReady()
Return whether the reference or exception have been set.- Returns:
- true if has been set. else false
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peek
public java.lang.Object peek()
Access the reference, even if not ready- Returns:
- current value
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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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