MapReduce Reducer Assignment

Motivation

Collector is fundamental to the MapReduce Framework lab.

Background

After much debate, we decided to go with interface Collector<T,A,R> from the standard Java streams framework as the basis for the MapReduce assignment.

It might have been slightly less confusing at the outset if we provided our own custom interface. Imaging the mythical non-existant interface below:

public interface Reducer<V, A, R> {
	A createMutableContainer();
	void accumulate(A container, V item);
	A combine(A containerA, A containerB);
	R reduce(A container);
}

class MutableInt

Mythical Reducer:

public class CollectorReducerAdapter<V, A, R> implements Reducer<V, A, R> {
	private final Collector<V,A,R> collector;
	public CollectorReducerAdapter(Collector<V,A,R> collector) {
		this.collector = collector;
	}
	@Override
	public A createMutableContainer() {
		return collector.supplier().get();
	}
	@Override
	public void accumulate(A container, V item) {
		collector.accumulator().accept(container, item);
	}
	@Override
	public A combine(A containerA, A containerB) {
		return collector.combiner().apply(containerA, containerB);
	}
	@Override
	public R reduce(A container) {
		return collector.finisher().apply(container);
	}
}

Code To Implement

ClassicReducer

class:	ClassicReducer.java
methods:	supplier accumulator combiner
package:	mapreduce.collector.studio
source folder:	student/src/main/java

IntSumCollector

class:	IntSumCollector.java
methods:	supplier accumulator combiner finisher
package:	mapreduce.collector.intsum.studio
source folder:	student/src/main/java

Testing Your Solution

Correctness

class:	CollectorStudioTestSuite.java
package:	mapreduce
source folder:	testing/src/test/java