IncrementalTask.java from DrJava at Krugle
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/*BEGIN_COPYRIGHT_BLOCK*
PLT Utilities BSD License
Copyright (c) 2007 JavaPLT group at Rice University
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Developed by: Java Programming Languages Team
Rice University
http://www.cs.rice.edu/~javaplt/
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package edu.rice.cs.plt.concurrent;
import java.util.Iterator;
import edu.rice.cs.plt.lambda.Thunk;
/**
* A thunk that performs incremental computation. Clients will repeatedly invoke {@link #step}
* until {@link #isFinished} is {@code true}, signifying that the result has been computed.
* {@link #value} need only be supported <em>after</em> the task has completed.
* @param I The type of the incremental result (may be {@link Void} if there is no useful
* intermediate result)
* @param R The type of the final result (may be {@link Void} if the task has no useful final result)
*/
public interface IncrementalTask<I, R> extends Thunk<R> {
/**
* Whether the final result is ready. As long as this returns {@code false}, {@link #step} will
* be invoked; after returning {@code true}, only {@link #value} will be invoked.
*/
public boolean isFinished();
/** Perform a step in the computation. Undefined when {@link #isFinished} is {@code true}. */
public I step();
/** Produce the final result of the task. Undefined when {@link #isFinished} is {@code false}. */
public R value();
}
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