A.java

package p;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import edu.cuny.hunter.streamrefactoring.annotations.*;
import p.A.Widget.Color;

public class A {

	static class Widget {
		enum Color {
			RED,
			BLUE,
			GREEN,
			PINK,
			ORANGE,
			YELLOW
		};

		public Color getColor() {
			return this.getColor();
		}
	}

	@EntryPoint
	void m() {
		// an "unordered" collection of widgets.
		Collection<Widget> unorderedWidgets = new HashSet<>();
		// populate the collection ...

		Map<Color, List<Widget>> widgetsByColor = unorderedWidgets.stream()
				.collect(Collectors.groupingBy(Widget::getColor));
	}
}