ACM Airports problem

ACMAirport.java

import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;


public class ACMAirport {

	// Earth's radius
	public static final double R = 3958.75;

	/**
	 * Represents the Latitude and Longitude of a point on Earth's surface,
	 * in radians.
	 *
	 */
	private static class Coordinate{
		private final double lat;
		private final double lon;
		public Coordinate(int latDeg, int latMin, int latSec, String ns, int lonDeg, int lonMin, int lonSec, String ew){
			// latitude is given in degrees, minutes, seconds; convert to decimal
			double lat = latDeg;
			lat += latMin / 60.0;
			lat += latSec / (60.0 * 60.0);
			// adjust sign
			switch(ns){
			case "n":
			case "N":
				break;
			case "s":
			case "S":
				lat = -lat;
				break;
			default:
				throw new IllegalArgumentException("ns must be n or s, got " + ns);
			}
			// store
			this.lat = Math.toRadians(lat);

			// likewise
			double lon = lonDeg;
			lon += lonMin / 60.0;
			lon += lonSec / (60.0 * 60.0);
			switch(ew){
			case "e":
			case "E":
				break;
			case "w":
			case "W":
				lon = -lon;
				break;
			default:
				throw new IllegalArgumentException("ew must be e or w, got " + ew);
			}
			this.lon = Math.toRadians(lon);
		}
		public double getLon() {
			return lon;
		}
		public double getLat() {
			return lat;
		}
		
	}
	
	// map from airport code to airport's location
	private static final Map<String, Coordinate> airportLocations = new HashMap<>();
	
	/**
	 * Insert an airport into airportLocations.
	 * 
	 * line contains: 
	 * 		the airport code; 
	 * 		degrees, minutes, seconds latitude;
	 * 		and degrees, minutes, seconds longitude.
	 * eg "MAD 40 28 20 N 03 33 39 W"
	 * 
	 * @param line A String containing the airport code
	 */
	private static void insert(String line){
		// Using a regex would probably allow for better error checking
		String[] tokens = line.split(" ");
		String code = tokens[0];
		int latDeg = Integer.parseInt( tokens[1]);
		int latMin = Integer.parseInt( tokens[2]);
		int latSec = Integer.parseInt( tokens[3]);
		String ns = tokens[4];
		int lonDeg = Integer.parseInt( tokens[5]);
		int lonMin = Integer.parseInt( tokens[6]);
		int lonSec = Integer.parseInt( tokens[7]);
		String ew = tokens[8];
		Coordinate c = new Coordinate(latDeg, latMin, latSec, ns, lonDeg, lonMin, lonSec, ew);
		airportLocations.put(code, c);
	}

	/**
	 * Read test data from System.in
	 * @param args
	 */
	public static void main(String[] args) {
		String data = 
		"MAD 40 28 20 N 03 33 39 W\n"
		+"CMN 33 22 04 N 07 35 16 W\n"
		+"RAK 31 36 24 N 08 02 10 W\n"
		+"HNL 21 18 57 N 157 55 36 W\n"
		+"YYZ 43 40 38 N 79 37 50 W\n"
		+"FRA 50 01 35 N 08 32 35 E\n"
		+"LAS 36 04 49 N 115 09 08 W\n"
		+"LAX 33 56 33 N 118 24 29 W\n"
		+"---\n"
		+"LAS LAX HNL LAX LAS\n"
		+"LAX YYZ FRA CMN\n"
		+"LAX MAD RAK\n"
		;
		/*
MAD 40 28 20 N 03 33 39 W
CMN 33 22 04 N 07 35 16 W
RAK 31 36 24 N 08 02 10 W
HNL 21 18 57 N 157 55 36 W
YYZ 43 40 38 N 79 37 50 W
FRA 50 01 35 N 08 32 35 E
LAS 36 04 49 N 115 09 08 W
LAX 33 56 33 N 118 24 29 W
---
LAS LAX HNL LAX LAS
LAX YYZ FRA CMN
LAX MAD RAK
		 */
		Scanner in = new Scanner(System.in);
		//Scanner in = new Scanner(data);
		String line;
		
		// create airport location table
		while(in.hasNextLine() && !(line = in.nextLine()).equals("---")){
			insert(line.trim());
		}
		
		// build a thread pool to compute distances concurrently
		// C++ can omit this
		int cores = Runtime.getRuntime().availableProcessors();
		ExecutorService pool = Executors.newFixedThreadPool(cores);
		CompletionService<Double> cs = new ExecutorCompletionService<>(pool);
		List<Future<Double>> results = new LinkedList<>();
		
		// read paths and begin computing distances
		while(in.hasNextLine()){
			DistanceTask task = new DistanceTask(in.nextLine().trim());
			// executes task.call() in tread pool
			// C++ should just do cout << task.call() << endl;
			results.add(cs.submit(task));
		}
		
		// results are read in the same order they are submitted
		for(Future<Double> result : results){
			try {
				System.out.println(Math.round(result.get()));
			} catch (InterruptedException | ExecutionException e) {
				e.printStackTrace();
			}
		}
		
		pool.shutdown();
		
		in.close();
	}
	
	private static class DistanceTask implements Callable<Double>{
		// space-delimited list of airport codes
		private final String line;

		public DistanceTask(String line) {
			this.line = line;
		}

		/**
		 * Computes the total distance of a list of airport connections
		 *
		 */
		@Override
		public Double call() throws Exception {
			String[] airports = line.split(" ");
			double distance = 0.0;
			Coordinate prevCoord = null;
			Coordinate curCoord = airportLocations.get(airports[0]);
			
			for(int i = 1; i < airports.length; i++){
				prevCoord = curCoord;
				curCoord = airportLocations.get(airports[i]);
				distance += greatCircleDistance(prevCoord, curCoord);
			}
			return distance;
		}

		/**
		 * Calculate the Great-Circle distance between from and to.
		 * https://en.wikipedia.org/wiki/Great-circle_distance
		 * 
		 * @param from latitude and longitude of departure
		 * @param to   latitude and longitude of destination
		 * @return     the great-circle distance
		 */
		private double greatCircleDistance(Coordinate from, Coordinate to) {
			double deltalon = to.getLon() - from.getLon();
			double theta = Math.acos(
					Math.sin(from.getLat()) * Math.sin(to.getLat())
					+ Math.cos(from.getLat()) * Math.cos(to.getLat()) * Math.cos(deltalon));
			return R * theta;
		}

		
	}

}

https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&category=669&page=show_problem&problem=5147