Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;

import java.util.Calendar;

import java.util.Locale;
import java.util.TimeZone;

public class Main {
    /***
     * Fetch the estimate current time of arrival at the destination
     * @param timeZone - The timezone at the destination
     * @param distance - how far to the target
     * @param speed - how fast we are moving
     * @param bearing - direction to target
     * @param heading - direction of movement
     * @return String - "HH:MM" current time at the target
     */
    public static String calculateEta(TimeZone timeZone, double distance, double speed, double bearing,
            double heading) {

        // fetch the raw ETE
        int eteRaw = fetchRawEte(distance, speed, bearing, heading);

        // If no speed, or the eteRaw is meaningless, then return an empty display string
        if (0 == speed || eteRaw == -1) {
            return "--:--";
        }

        // Break the hours and minutes out
        int eteHr = eteRaw / 100;
        int eteMin = eteRaw % 100;

        // Hours greater than 99 are not displayable
        if (eteHr > 99) {
            return "XX:XX";
        }

        // Get the current local time hours and minutes
        int etaHr = Calendar.getInstance().get(Calendar.HOUR_OF_DAY);
        int etaMin = Calendar.getInstance().get(Calendar.MINUTE);

        // Add in our ETE to the current time, accounting for rollovers
        etaMin += eteMin; // Add the estimated minutes enroute to "now"
        if (etaMin > 59) {
            etaMin -= 60;
            etaHr++;
        } // account for minute rollover
        etaHr += eteHr; // Now add the hours enroute
        while (etaHr > 23) {
            etaHr -= 24;
        } // account for midnight rollover

        // Format the hours and minutes
        String strHr = String.format(Locale.getDefault(), "%02d", etaHr);
        String strMn = String.format(Locale.getDefault(), "%02d", etaMin);

        // Build string of return
        return strHr + ":" + strMn;
    }

    /***
     * Fetch the raw estimated time enroute given the input parameters
     * @param distance - how far to the target
     * @param speed - how fast we are moving
     * @param bearing - direction to target
     * @param heading - direction of movement
     * @return int value of HR * 100 + MIN for the ete, -1 if not applicable
     */
    private static int fetchRawEte(double distance, double speed, double bearing, double heading) {
        // We can't assume that we are heading DIRECTLY for the destination, so 
        // we need to figure out the multiply factor by taking the COS of the difference
        // between the bearing and the heading.
        double angDif = angularDifference(heading, bearing);

        // If the difference is 90 or greater, then ETE means nothing as we are not
        // closing on the target
        if (angDif >= 90)
            return -1;

        // Calculate the actual relative speed closing on the target
        double xFactor = Math.cos(angDif * Math.PI / 180);
        double eteTotal = distance / (speed * xFactor);

        // Break that down into hours and minutes
        int eteHr = (int) eteTotal;
        int eteMin = (int) Math.round((eteTotal - (double) eteHr) * 60);

        // account for the minutes being 60
        if (eteMin >= 60) {
            eteHr++;
            eteMin -= 60;
        }

        // Return with our estimate
        return eteHr * 100 + eteMin;
    }

    /** Calculate the absolute angular difference between the two headings
     * 
     * @param hdg angle 1 in degrees (typically the heading)
     * @param brg angle 2 in degrees (typically the bearing)
     * @return difference between hdg and brg in degrees
     */
    public static double angularDifference(double hdg, double brg) {
        double absDiff = Math.abs(hdg - brg);
        if (absDiff > 180) {
            return 360 - absDiff;
        }
        return absDiff;
    }
}