Java Unix time unixDateToString(int date)

Description

Helper for CAST({date} AS VARCHAR(n)).

License

Apache License

Declaration

public static String unixDateToString(int date) 

Method Source Code

//package com.java2s;
/*//from   w  ww  . j av a2s  .c  om
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

public class Main {
    /** The julian date of the epoch, 1970-01-01. */
    public static final int EPOCH_JULIAN = 2440588;

    /** Helper for CAST({date} AS VARCHAR(n)). */
    public static String unixDateToString(int date) {
        final StringBuilder buf = new StringBuilder(10);
        unixDateToString(buf, date);
        return buf.toString();
    }

    private static void unixDateToString(StringBuilder buf, int date) {
        julianToString(buf, date + EPOCH_JULIAN);
    }

    private static void julianToString(StringBuilder buf, int julian) {
        // this shifts the epoch back to astronomical year -4800 instead of the
        // start of the Christian era in year AD 1 of the proleptic Gregorian
        // calendar.
        int j = julian + 32044;
        int g = j / 146097;
        int dg = j % 146097;
        int c = (dg / 36524 + 1) * 3 / 4;
        int dc = dg - c * 36524;
        int b = dc / 1461;
        int db = dc % 1461;
        int a = (db / 365 + 1) * 3 / 4;
        int da = db - a * 365;

        // integer number of full years elapsed since March 1, 4801 BC
        int y = g * 400 + c * 100 + b * 4 + a;
        // integer number of full months elapsed since the last March 1
        int m = (da * 5 + 308) / 153 - 2;
        // number of days elapsed since day 1 of the month
        int d = da - (m + 4) * 153 / 5 + 122;
        int year = y - 4800 + (m + 2) / 12;
        int month = (m + 2) % 12 + 1;
        int day = d + 1;
        int4(buf, year);
        buf.append('-');
        int2(buf, month);
        buf.append('-');
        int2(buf, day);
    }

    private static void int4(StringBuilder buf, int i) {
        buf.append((char) ('0' + (i / 1000) % 10));
        buf.append((char) ('0' + (i / 100) % 10));
        buf.append((char) ('0' + (i / 10) % 10));
        buf.append((char) ('0' + i % 10));
    }

    private static void int2(StringBuilder buf, int i) {
        buf.append((char) ('0' + (i / 10) % 10));
        buf.append((char) ('0' + i % 10));
    }
}

Related

1. getUnixEpochDateTime()
2. getUnixTime(Date date)
3. getUnixTimeByDate(Date date)
4. unix2afpTime(long ut)
5. unixTime()
6. unixtime()
7. unixTimestamp(int year, int month, int day, int hour, int minute, int second)
8. unixTimestampToString(long timestamp)