Test.java

import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.IntStream;

public class Test{


	public static <T> Predicate<T> distinctByKey( Function<? super T, Object> keyExtractor) {
		Map<Object, Boolean> map = new HashMap<>();
		return t -> map.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
	}
	
	
	public static void main(String[] args) {
	

		List<Member> memberList = new ArrayList<>();
		
		
		IntStream.range(13, 17)
		.forEach(i -> {
			memberList.add(new Member("aa" + i, i));
		});
		
		IntStream.range(10, 20)
		.forEach(i -> {
			memberList.add(new Member("unknown_" + i, i));
		});
		
		
		
		
		memberList.stream()
		.filter(distinctByKey(m -> m.getAge()))
		.sorted( new Comparator<Member>() {
			public int compare(Member o1, Member o2) {
				// TODO Auto-generated method stub
				return Long.compare(o1.getAge(), o2.getAge());
			}
		})
		.forEach(System.out::println);
		

		
	}
	


	public static class Member {
		
		
		private String name;
		private long age;
		
		
		public Member(String name, long age) {
			super();
			this.name = name;
			this.age = age;
		}
		
		public String getName() {
			return name;
		}
		public void setName(String name) {
			this.name = name;
		}
		public long getAge() {
			return age;
		}
		public void setAge(long age) {
			this.age = age;
		}

		@Override
		public String toString() {
			return "Member [name=" + name + ", age=" + age + "]";
		}
		
	}

	
}