Here you can find the source of formatDateTime(long d)
public static String formatDateTime(long d)
//package com.java2s; //License from project: Apache License import java.text.SimpleDateFormat; import java.util.Calendar; import java.util.Date; public class Main { private static String DATETIME_FORMAT = "yyyy-MM-dd HH:mm"; private static final int[] DAYS = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }; /**/*from w ww.ja va 2s. com*/ * Convert date and time to string like "yyyy-MM-dd HH:mm". */ public static String formatDateTime(Date d) { return new SimpleDateFormat(DATETIME_FORMAT).format(d); } /** * Convert date and time to string like "yyyy-MM-dd HH:mm". */ public static String formatDateTime(long d) { return new SimpleDateFormat(DATETIME_FORMAT).format(d); } public static String format(int hour, int minute, String format) { if ("HH-mm".equals(format)) { StringBuilder sb = new StringBuilder(5); if (hour < 10) sb.append('0'); sb.append(hour).append(':'); if (minute < 10) sb.append('0'); return sb.append(minute).toString(); } Calendar c = Calendar.getInstance(); c.set(Calendar.HOUR_OF_DAY, hour); c.set(Calendar.MINUTE, minute); c.set(Calendar.SECOND, 0); return new SimpleDateFormat(format).format(c.getTime()); } public static String format(int year, int month, int day, String format) { if ("MM-dd".equals(format)) { StringBuilder sb = new StringBuilder(5); return sb.append(month).append('-').append(day).toString(); } if ("yyyy-MM-dd".equals(format)) { StringBuilder sb = new StringBuilder(10); return sb.append(year).append('-').append(month).append('-').append(day).toString(); } Calendar c = getCalendar(year, month, day); return new SimpleDateFormat(format).format(c.getTime()); } /** * Return day's year, month(1-12), day(1-31), week(0-6, for SUN, MON, ... SAT), hour, minute, second. */ public static int[] getTime(long t) { Calendar c = Calendar.getInstance(); c.setTimeInMillis(t); return getTime(c); } /** * Return day's year, month(1-12), day(1-31), week(0-6, for SUN, MON, ... SAT), hour, minute, second. */ public static int[] getTime(Calendar c) { int week = c.get(Calendar.DAY_OF_WEEK) - 1; if (week == 0) week = 7; return new int[] { c.get(Calendar.YEAR), c.get(Calendar.MONTH) + 1, c.get(Calendar.DAY_OF_MONTH), week, c.get(Calendar.HOUR_OF_DAY), c.get(Calendar.MINUTE), c.get(Calendar.SECOND) }; } /** * Get Calendar instance by specified year, month and day. * * @param year 4-digit year. * @param month Month range is 1-12. * @param day Day range is 1-?, end depends on year and month. * @return A Calendar instance. */ public static Calendar getCalendar(int year, int month, int day) { if (year < 2000 || year > 2100) throw new IllegalArgumentException(); if (month < 1 || month > 12) throw new IllegalArgumentException(); if (day < 1) throw new IllegalArgumentException(); if (month == 2 && isLeapYear(year)) { if (day > 29) throw new IllegalArgumentException(); } else { if (day > DAYS[month - 1]) throw new IllegalArgumentException(); } month--; Calendar c = Calendar.getInstance(); c.set(Calendar.YEAR, year); c.set(Calendar.MONTH, month); c.set(Calendar.DAY_OF_MONTH, day); c.set(Calendar.HOUR_OF_DAY, 0); c.set(Calendar.MINUTE, 0); c.set(Calendar.SECOND, 0); c.set(Calendar.MILLISECOND, 0); return c; } public static boolean isLeapYear(int year) { if (year % 100 == 0) { return year % 400 == 0; } return year % 4 == 0; } }