TimeParser.java

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public final class TimeParser {

    private static final long MINUTE = 60;
    private static final long HOUR = MINUTE * 60;
    private static final long DAY = HOUR * 24;
    private static final long WEEK = DAY * 7;
    private static final long MONTH = DAY * 30;
    private static final long YEAR = DAY * 365;

    public static Time toSeconds(String from) {
        List<String> letters = Arrays.asList(from.split("\\d")).stream().filter(string -> !string.isEmpty()).collect(Collectors.toList());
        List<String> values = Arrays.asList(from.split("\\D"));
        if (letters.size() != values.size())
            return new Time(0);
        long out = 0L;
        for (int i = 0; i < letters.size(); i++) {
            long value = Long.parseLong(values.get(i));
            switch (letters.get(i)) {
                case "s":
                    out += value;
                    break;
                case "m":
                    out += MINUTE * value;
                    break;
                case "h":
                    out += HOUR * value;
                    break;
                case "d":
                    out += DAY * value;
                    break;
                case "w":
                    out += WEEK * value;
                    break;
                case "M":
                    out += MONTH * value;
                    break;
                case "y":
                    out += YEAR * value;
                    break;
                default:
                    continue;
            }
        }
        return new Time(out);
    }

    public static String format(long seconds) {
        String out = "";
        boolean hasPrev = false;
        int holder;
        if (seconds >= YEAR) {
            hasPrev = true;
            holder = (int) (seconds / YEAR);
            out += holder + (holder > 1 ? " years " : " year ");
            seconds -= holder * YEAR;
        }
        if (seconds >= MONTH) {
            hasPrev = true;
            holder = (int) (seconds / MONTH);
            out += holder + (holder > 1 ? " months " : " month ");
            seconds -= holder * MONTH;
        }
        if (seconds >= WEEK) {
            hasPrev = true;
            holder = (int) (seconds / WEEK);
            out += holder + (holder > 1 ? " weeks " : " week ");
            seconds -= holder * WEEK;
        }
        if (seconds >= DAY) {
            hasPrev = true;
            holder = (int) (seconds / DAY);
            out += holder + (holder > 1 ? " days " : " day ");
            seconds -= holder * DAY;
        }
        if (seconds >= HOUR) {
            hasPrev = true;
            holder = (int) (seconds / HOUR);
            out += holder + (holder > 1 ? " hours " : " hour ");
            seconds -= holder * HOUR;
        }
        if (seconds >= MINUTE) {
            hasPrev = true;
            holder = (int) (seconds / MINUTE);
            out += holder + (holder > 1 ? " minutes " : " minute ");
            seconds -= holder * MINUTE;
        }
        if (seconds > 0) {
            out += (hasPrev ? "and " : "") + seconds + (seconds > 1 ? " seconds" : " second");
            hasPrev = true;
        }
        if (!hasPrev) return "0 seconds";
        return out.trim();
    }


}