import static java.util.Comparator.comparing;
import static java.util.stream.Collectors.collectingAndThen;
import static java.util.stream.Collectors.groupingBy;
import static java.util.stream.Collectors.maxBy;
import static java.util.stream.Collectors.toList;

import java.util.ArrayList;
import java.util.List;
import java.util.Optional;

public class GroupByGetMaxToListSort {

	private static List<Obj> raw() {
		final List<Obj> raw = new ArrayList<>();
		raw.add(new Obj("a", 6));
		raw.add(new Obj("a", 4));
		raw.add(new Obj("b", 8));
		raw.add(new Obj("c", 1));
		raw.add(new Obj("c", 11));
		raw.add(new Obj("b", 3));
		raw.add(new Obj("a", 7));
		raw.add(new Obj("c", 5));
		raw.add(new Obj("d", 0));
		return raw;
	}

	public static void main(String[] args) {
		final List<Obj> result = raw().stream()
				.collect(groupingBy(Obj::getType, collectingAndThen(maxBy(comparing(Obj::getVal)), Optional::get)))
				.values().stream().sorted(comparing(Obj::getVal)).collect(toList());
		System.out.println(result);
		// output is [{"type":"d", val":"0}, {"type":"a", val":"7}, {"type":"b", val":"8}, {"type":"c", val":"11}]
	}

}

class Obj {
	private String type;
	private int val;

	public Obj(String type, int val) {
		this.type = type;
		this.val = val;
	}

	public String getType() {
		return type;
	}

	public void setType(String type) {
		this.type = type;
	}

	public int getVal() {
		return val;
	}

	public void setVal(int val) {
		this.val = val;
	}

	@Override
	public String toString() {
		return String.format("{\"type\":\"%s\", val\":\"%s}", type, val);
	}

}