45 lines
1.6 KiB
Java
45 lines
1.6 KiB
Java
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package com.iluwatar.halfsynchalfasync;
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import java.util.concurrent.Callable;
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/**
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* Represents some computation that is performed asynchronously and its result.
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* The computation is typically done is background threads and the result is posted
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* back in form of callback. The callback does not implement {@code isComplete}, {@code cancel}
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* as it is out of scope of this pattern.
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*
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* @param <O> type of result
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*/
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public interface AsyncTask<O> extends Callable<O> {
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/**
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* Is called in context of caller thread before call to {@link #call()}. Large
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* tasks should not be performed in this method as it will block the caller thread.
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* Small tasks such as validations can be performed here so that the performance penalty
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* of context switching is not incurred in case of invalid requests.
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*/
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void onPreCall();
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/**
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* A callback called after the result is successfully computed by {@link #call()}. In our
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* implementation this method is called in context of background thread but in some variants,
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* such as Android where only UI thread can change the state of UI widgets, this method is called
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* in context of UI thread.
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*/
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void onPostCall(O result);
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/**
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* A callback called if computing the task resulted in some exception. This method
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* is called when either of {@link #call()} or {@link #onPreCall()} throw any exception.
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*
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* @param throwable error cause
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*/
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void onError(Throwable throwable);
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/**
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* This is where the computation of task should reside. This method is called in context
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* of background thread.
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*/
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@Override
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O call() throws Exception;
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}
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