I have this code and it shown an error: java.lang.NullPointerException at FastestTrain.main(FastestTrain.java:77)

Please help me fix the error.

The code contains 3 classes:

//FastestTrain Class

import java.io.File; import java.io.FileNotFoundException; import java.util.Scanner;

public class FastestTrain {

static final String FILE_NAME = "trains.txt";

/** * This method gets a train list from the file * * @throws FileNotFoundException * - if file not found */ static Train[] getTrains() throws FileNotFoundException { // Scanner to read from the file Scanner inFile = new Scanner(new File(FILE_NAME));

// Array to hold train details Train[] trains = null;

// Read file // Get number of trains if (inFile.hasNextInt()) { int numTrains = inFile.nextInt();

// Get distance if (inFile.hasNextInt()) { int distance = inFile.nextInt();

// Consume the newline character at the end of distance inFile.nextLine();

// Array to hold train details trains = new Train[numTrains]; int count = 0;

// Read train details while (inFile.hasNextLine()) {

// Get train name String name = inFile.nextLine().trim();

// Get departure time String[] depTime = inFile.nextLine().trim().split("\\s+");

// Get arrival time String[] arrTime = inFile.nextLine().trim().split("\\s+");

// Add Train to array trains[count++] = new Train(name, new Time(Integer.parseInt(depTime[0]), Integer.parseInt(depTime[1])), new Time(Integer.parseInt(arrTime[0]), Integer.parseInt(arrTime[1])), distance); } } }

// Close scanner inFile.close();

return trains; }

public static void main(String[] args) {

try { // Get train list from file Train[] trains = getTrains();

// Find fastest train int index = 0; Time fastestTime = trains[0].travelTime(trains[0].getArrival()); // System.out.println(trains[0] + " "); // For debugging

for (int i = 1; i < trains.length; i++) { // Get travel time of train i Time travelTime = trains[i].travelTime(trains[i].getArrival());

// Check if travel time is less than fastestTime if ((travelTime.getHour() < fastestTime.getHour()) || ((travelTime.getHour() == fastestTime.getHour()) && (travelTime.getMinute() < fastestTime.getMinute()))) { fastestTime = travelTime; index = i; } // System.out.println(trains[i] + " "); // For debugging }

// Display fastest train System.out.println("Fastest train as per travel time: " + trains[index]);

} catch (FileNotFoundException fnfe) { System.out.println("File not found: " + FILE_NAME); } }

}

//Time Class

public class Time {

// Instance variables private Integer hour; private Integer minute;

/** * Parameterized constructor * * @param hour * - hour * @param minute * - minute */ public Time(Integer hour, Integer minute) { this.hour = hour; this.minute = minute; }

/** * This method returns the hour * * @return the hour */ public Integer getHour() { return hour; }

/** * This method returns the minute * * @return the minute */ public Integer getMinute() { return minute; }

/** * This method sets the hour * * @param hour * the hour to set */ public void setHour(Integer hour) { this.hour = hour; }

/** * This method sets the minute * * @param minute * the minute to set */ public void setMinute(Integer minute) { this.minute = minute; }

/** * This method calculates and returns the time between this time and aTime * * @param aTime * - Time * @return - time between this time and aTime */ public Time timeBetween(Time aTime) { // Check whether train arrives next day if ((this.hour > aTime.hour) || ((this.hour == aTime.hour) && (this.minute > aTime.minute))) {

// Get hours remaining for the day to end int hoursRemaining = 24 - this.hour;

// Subtract this.minute from hoursRemaining // i.e. get the total minutes remaining for the day to end int minutesRemaining = (hoursRemaining * 60) - this.minute;

// Calculate minutes elapsed after the next day begins int minutesElpased = (aTime.hour * 60) + aTime.minute;

// Find sum of minutes int totalMinutes = minutesRemaining + minutesElpased;

// Return time between this time and aTime return new Time(totalMinutes / 60, totalMinutes % 60);

} else {

// Get hour difference in minutes int hourDiffInMin = (aTime.hour - this.hour) * 60;

// Subtract this.minute from hourDiffInMin hourDiffInMin -= this.minute;

// Add aTime.minute to hourDiffInMin hourDiffInMin += aTime.minute;

return new Time(hourDiffInMin / 60, hourDiffInMin % 60); } }

/** * This method checks if t is less than zero. If yes then appends t with a * zero on the left and returns the String, else returns t as a string * * @param t * - integer to be checked * @return - formatted integer t */ public String zeroTime(Integer t) { if (t < 10) return "0" + t; else return "" + t; }

@Override public String toString() { return zeroTime(hour) + ":" + zeroTime(minute); } }

//Train Class

public class Train {

// Instance variables private String name; private Time departure; private Time arrival; private Integer distance;

/** * Parameterized constructor * * @param name * - train name * @param departure * - departure time of train * @param arrival * - arrival time of train at the destination * @param distance * - distance from source station to the destination station */ public Train(String name, Time departure, Time arrival, Integer distance) { this.name = name; this.departure = departure; this.arrival = arrival; this.distance = distance; }

/** * This method returns the departure time * * @return the departure */ public Time getDeparture() { return departure; }

/** * This method returns the arrival time * * @return the arrival */ public Time getArrival() { return arrival; }

/** * This method returns the distance * * @return the distance */ public Integer getDistance() { return distance; }

/** * This method sets the departure time * * @param departure * the departure to set */ public void setDeparture(Time departure) { this.departure = departure; }

/** * This method sets the arrival time * * @param arrival * the arrival to set */ public void setArrival(Time arrival) { this.arrival = arrival; }

/** * This method sets the distance * * @param distance * the distance to set */ public void setDistance(Integer distance) { this.distance = distance; }

/** * This method finds the average speed of the train * * @return - the average speed of the train */ public Integer averageSpeed() { Time travelTime = travelTime(arrival);

return Math.round((distance / (travelTime.getHour() + (travelTime.getMinute() / 60.0f)))); }

/** * This method finds the time between departure and arrival time */ public Time travelTime(Time arrivalTime) { return departure.timeBetween(arrivalTime); }

public String toString() { return name + " " + "Departure " + departure + " " + "Arrival " + arrival + " " + "Travel Time " + travelTime(arrival) + " " + "Average speed " + averageSpeed() + " km/h"; } }

The txt file is:

650 10 Night Express 23 55 8 15 Red Arrow 22 10 7 45 Star 10 30 19 25 Comfort 11 45 20 40 Budget 5 50 18 55 Day Rocket 11 55 16 00 Super Star 12 20 16 48 Good Morning 21 20 8 45 Best Choice 20 00 7 25 Sunrise 21 30 5 40