DateHelpers.java

/*
Copyright 2011-2016 Google Inc. All Rights Reserved.

Licensed 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.
*/
package com.google.security.zynamics.zylib.date;

import java.text.DateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Locale;

import com.google.common.base.Preconditions;

/**
 * Helper class that provides quick access to common date/time functions.
 */
public class DateHelpers {
  public static String formatDate(final Date date) {
    Preconditions.checkNotNull(date, "Error: Date argument can't be null.");

    return DateFormat.getDateInstance().format(date);
  }

  /**
   * Formats a date string regarding the given locale.
   * 
   * @param date The date to format.
   * @param type Defines the display type of month
   * @param locale The given locale.
   * 
   * @return The data string.
   */
  public static String formatDate(final Date date, final int type, final Locale locale) {
    Preconditions.checkNotNull(date, "Error: Date argument can't be null.");
    Preconditions.checkNotNull(locale, "Error: Locale argument can't be null.");

    final String s =
        String.format("%s %s", DateFormat.getDateInstance(type, locale).format(date), DateFormat
            .getTimeInstance(type, locale).format(date));

    return s;
  }

  /**
   * Formats a date string using the currently selected locale.
   * 
   * @param date The date to format.
   * 
   * @return The data string.
   */
  public static String formatDateTime(final Date date) {
    Preconditions.checkNotNull(date, "Error: Date argument can't be null.");

    return DateFormat.getDateTimeInstance().format(date);
  }

  public static String formatTime(final Date date) {
    Preconditions.checkNotNull(date, "Error: Date argument can't be null.");

    return DateFormat.getTimeInstance().format(date);
  }

  /**
   * Returns the current date.
   * 
   * @return The current date.
   */
  public static Date getCurrentDate() {
    return Calendar.getInstance().getTime();
  }

  /**
   * Returns the current date in string form.
   * 
   * @return A string that contains the current date.
   */
  public static String getCurrentDateString() {
    return formatDateTime(Calendar.getInstance().getTime());
  }

  /**
   * Extracts the date from a user defined date String.
   * 
   * @param dateString The date string to extract the date from.
   * @param format The format of the date string (e.g: MM-DD-YYYY)
   * 
   * @return The current date.
   */
  public static Date getDate(final String dateString, final String format) {
    Preconditions
        .checkArgument(dateString.length() == format.length(),
            "Date string format exception. Format string must have the same length as the date string.");

    String day = "";
    String month = "";
    String year = "";

    for (int i = 0; i < format.length(); ++i) {
      final char chr = format.charAt(i);

      if (chr == 'D') {
        day += dateString.charAt(i);
      } else if (chr == 'M') {
        month += dateString.charAt(i);
      } else if (chr == 'Y') {
        year += dateString.charAt(i);
      }
    }

    Preconditions.checkArgument(day.length() == 2,
        "Date string format exception. Date string's day field must have two chars.");
    Preconditions.checkArgument(month.length() == 2,
        "Date string format exception. Date string's month field must have two chars.");
    Preconditions.checkArgument(year.length() == 4,
        "Date string format exception. Date string's years field must have four chars.");

    final int iday = Integer.parseInt(day);
    final int imonth = Integer.parseInt(month) - 1;
    final int iyear = Integer.parseInt(year);

    final GregorianCalendar calendar = new GregorianCalendar(iyear, imonth, iday);

    return calendar.getTime();
  }
}