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*
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* accompanied this code).
*
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package java.util.stream;
import java.util.Spliterator;
/**
* An operation in a stream pipeline that takes a stream as input and produces
* a result or side-effect. A {@code TerminalOp} has an input type and stream
* shape, and a result type. A {@code TerminalOp} also has a set of
* <em>operation flags</em> that describes how the operation processes elements
* of the stream (such as short-circuiting or respecting encounter order; see
* {@link StreamOpFlag}).
*
* <p>A {@code TerminalOp} must provide a sequential and parallel implementation
* of the operation relative to a given stream source and set of intermediate
* operations.
*
* @param <E_IN> the type of input elements
* @param <R> the type of the result
* @since 1.8
*/
interface TerminalOp<E_IN, R> {
/**
* Gets the shape of the input type of this operation.
*
* @implSpec The default returns {@code StreamShape.REFERENCE}.
*
* @return StreamShape of the input type of this operation
*/
default StreamShape inputShape() { return StreamShape.REFERENCE; }
/**
* Gets the stream flags of the operation. Terminal operations may set a
* limited subset of the stream flags defined in {@link StreamOpFlag}, and
* these flags are combined with the previously combined stream and
* intermediate operation flags for the pipeline.
*
* @implSpec The default implementation returns zero.
*
* @return the stream flags for this operation
* @see StreamOpFlag
*/
default int getOpFlags() { return 0; }
/**
* Performs a parallel evaluation of the operation using the specified
* {@code PipelineHelper}, which describes the upstream intermediate
* operations.
*
* @implSpec The default performs a sequential evaluation of the operation
* using the specified {@code PipelineHelper}.
*
* @param helper the pipeline helper
* @param spliterator the source spliterator
* @return the result of the evaluation
*/
default <P_IN> R evaluateParallel(PipelineHelper<E_IN> helper,
Spliterator<P_IN> spliterator) {
if (Tripwire.ENABLED)
Tripwire.trip(getClass(), "{0} triggering TerminalOp.evaluateParallel serial default");
return evaluateSequential(helper, spliterator);
}
/**
* Performs a sequential evaluation of the operation using the specified
* {@code PipelineHelper}, which describes the upstream intermediate
* operations.
*
* @param helper the pipeline helper
* @param spliterator the source spliterator
* @return the result of the evaluation
*/
<P_IN> R evaluateSequential(PipelineHelper<E_IN> helper,
Spliterator<P_IN> spliterator);
}