MapScheduler.java

import java.time.Instant;
import java.time.LocalDateTime;
import java.util.*;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import java.time.Instant;
import java.util.*;
import java.util.stream.Collectors;
 
 
 class Scheduler<T>{

    HashMap<Date,T> dates;

    public Scheduler() {
        this.dates = new HashMap<Date, T>();
    }

     public void add(Date d,T t)
    {
       dates.putIfAbsent(d,t);
    }
    public boolean remove(Date d)
    {
        if(dates.containsKey(d)) {
            dates.remove(d);
            return true;
        }else return false;
    }


    public T next(){
        Date now = Date.from(Instant.from(LocalDateTime.now()));
        Optional<Date> date = dates.keySet().stream().filter(x->x.after(now)).sorted().findFirst();
        return dates.get(date.get());
    }

    public T last(){
        Date now = Date.from(Instant.now());
        Optional<Date> date = dates.keySet().stream().filter(x->x.before(now)).sorted().findFirst();
        return dates.get(date.get());
    }

     public ArrayList<T> getAll(Date begin, Date end){
        return ( ArrayList<T>) dates.keySet().
                stream().
                filter(x->x.after(begin)&&x.before(end)).
                sorted()
            .map(dates::get).
            collect(Collectors.toList()); 
    }

    public T getFirst(){
        Optional<Date> date = dates.keySet().stream().sorted(Comparator.naturalOrder()).findFirst();
        return dates.get(date.get());
    }
    public T getLast(){
        Optional<Date> date = dates.keySet().stream().sorted(Comparator.reverseOrder()).findFirst();
        return dates.get(date.get());
    }
    
    

}


public class SchedulerTest {
	
	
	public static void main(String[] args) {
		Scanner jin = new Scanner(System.in);
		int k = jin.nextInt();
		if ( k == 0 ) {
			Scheduler<String> scheduler = new Scheduler<String>();
			Date now = new Date();
			scheduler.add(new Date(now.getTime()-7200000), jin.next());
			scheduler.add(new Date(now.getTime()-3600000), jin.next());
			scheduler.add(new Date(now.getTime()-14400000), jin.next());
			scheduler.add(new Date(now.getTime()+7200000), jin.next());
			scheduler.add(new Date(now.getTime()+14400000), jin.next());
			scheduler.add(new Date(now.getTime()+3600000), jin.next());
			scheduler.add(new Date(now.getTime()+18000000), jin.next());
			System.out.println(scheduler.getFirst());
			System.out.println(scheduler.getLast());
		}
		if ( k == 3 ) { //test Scheduler with String
			Scheduler<String> scheduler = new Scheduler<String>();
			Date now = new Date();
			scheduler.add(new Date(now.getTime()-7200000), jin.next());
			scheduler.add(new Date(now.getTime()-3600000), jin.next());
			scheduler.add(new Date(now.getTime()-14400000), jin.next());
			scheduler.add(new Date(now.getTime()+7200000), jin.next());
			scheduler.add(new Date(now.getTime()+14400000), jin.next());
			scheduler.add(new Date(now.getTime()+3600000), jin.next());
			scheduler.add(new Date(now.getTime()+18000000), jin.next());
			System.out.println(scheduler.next());
			System.out.println(scheduler.last());
			ArrayList<String> res = scheduler.getAll(new Date(now.getTime()-10000000), new Date(now.getTime()+17000000));
			Collections.sort(res);
			for ( String t : res ) {
				System.out.print(t+" , ");
			}
		}
		if ( k == 4 ) {//test Scheduler with ints complex
			Scheduler<Integer> scheduler = new Scheduler<Integer>();
			int counter = 0;
			ArrayList<Date> to_remove = new ArrayList<Date>();
			
			while ( jin.hasNextLong() ) {
				Date d = new Date(jin.nextLong());
				int i = jin.nextInt();
				if ( (counter&7) == 0 ) {
					to_remove.add(d);
				}
				scheduler.add(d,i);
				++counter;
			}
			jin.next();
			
			while ( jin.hasNextLong() ) {
				Date l = new Date(jin.nextLong());
				Date h = new Date(jin.nextLong());
				ArrayList<Integer> res = scheduler.getAll(l,h);
				Collections.sort(res);
				System.out.println(l+" <: "+print(res)+" >: "+h);
			}
			System.out.println("test");
			ArrayList<Integer> res = scheduler.getAll(new Date(0),new Date(Long.MAX_VALUE));
			Collections.sort(res);
			System.out.println(print(res));
			for ( Date d : to_remove ) {
				scheduler.remove(d);
			}
			res = scheduler.getAll(new Date(0),new Date(Long.MAX_VALUE));
			Collections.sort(res);
			System.out.println(print(res));
		}
	}

	private static <T> String print(ArrayList<T> res) {
		if ( res == null || res.size() == 0 ) return "NONE";
		StringBuffer sb = new StringBuffer();
		for ( T t : res ) {
			sb.append(t+" , ");
		}
		return sb.substring(0, sb.length()-3);
	}

    
}