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Some helper classes i needed for several projects (Utils)
There is a newer version: 0.17
package se.wfh.libs.common.utils;

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

/**
 * Several Helper Methods to work with dates and times.
 * 
 * @author Simon Frankenberger
 * @since 0.2
 */
public final class DateTools {
	/** cached formatter for exports, allways american format */
	private static final SimpleDateFormat EXPORT_FORMATER = new SimpleDateFormat(
			"yyyy-MM-dd HH:mm:ss", Locale.ENGLISH);

	public static enum ConvertType {
		DATE,
		TIME,
		DATE_TIME,
		EXPORT,
	}

	/**
	 * Strips the seconds and milliseconds from the given calendar.
	 * 
	 * @param cal
	 *          The calendar to remove the fields
	 * @return The given calender without seconds and milliseconds
	 */
	public static Calendar cleanSeconds(final Calendar cal) {
		if (cal != null) {
			cal.set(Calendar.SECOND, 0);
			cal.set(Calendar.MILLISECOND, 0);
		}

		return cal;
	}

	/**
	 * Strips the seconds and milliseconds from the given date.
	 * 
	 * @param date
	 *          The date to remove the fields
	 * @return The given date without seconds and milliseconds
	 */
	public static Date cleanSeconds(final Date date) {
		if (date == null) {
			return null;
		}

		Calendar cal = new GregorianCalendar();
		cal.setTime(date);
		return cleanSeconds(cal).getTime();
	}

	/**
	 * Strips the time from the given calendar.
	 * 
	 * @param cal
	 *          The calendar to remove the fields
	 * @return The given calender without hours, minutes, seconds and milliseconds
	 */
	public static Calendar cleanTime(final Calendar cal) {
		if (cal != null) {
			cal.set(Calendar.HOUR_OF_DAY, 0);
			cal.set(Calendar.MINUTE, 0);
			cal.set(Calendar.SECOND, 0);
			cal.set(Calendar.MILLISECOND, 0);
		}

		return cal;
	}

	/**
	 * Strips the time from the given calendar.
	 * 
	 * @param date
	 *          The date to remove the fields
	 * @return The given calender without hours, minutes, seconds and milliseconds
	 */
	public static Date cleanTime(final Date date) {
		if (date == null) {
			return null;
		}

		Calendar cal = new GregorianCalendar();
		cal.setTime(date);
		return cleanTime(cal).getTime();
	}

	/**
	 * Parses the given string and extract the specified fields.
	 * 
	 * @param str
	 *          The string to parse.
	 * @param type
	 *          The fields to extract / The syntax of the string
	 * @return A calendar representing the string contents.
	 * @throws ParseException
	 *           If the given string is invalid.
	 */
	public static Calendar fromString(final String str, ConvertType type)
			throws ParseException {
		if (str == null) {
			return null;
		}

		final GregorianCalendar cal = new GregorianCalendar();
		final DateFormat format;

		switch (type) {
			case DATE:
				format = DateFormat.getDateInstance();
				break;
			case DATE_TIME:
				format = DateFormat.getDateTimeInstance();
				break;
			case EXPORT:
				synchronized (EXPORT_FORMATER) {
					format = EXPORT_FORMATER;
				}
				break;
			case TIME:
				format = DateFormat.getTimeInstance();
				break;
			default:
				format = null;
				break;
		}

		if (format == null) {
			return null;
		} else {
			synchronized (format) {
				cal.setTime(format.parse(str));
			}
		}

		return cal;
	}

	/**
	 * Format the given date and return a string representation of it.
	 * 
	 * @param date
	 *          The calender to format.
	 * @param type
	 *          The fields to export / The syntax of the resulting string
	 * @return A string representation of the date.
	 */
	public static String toString(final Date date, final ConvertType type) {
		if (date == null) {
			return null;
		}

		final DateFormat format;

		switch (type) {
			case DATE:
				format = DateFormat.getDateInstance();
				break;
			case DATE_TIME:
				format = DateFormat.getDateTimeInstance();
				break;
			case EXPORT:
				format = EXPORT_FORMATER;
				break;
			case TIME:
				format = DateFormat.getTimeInstance();
				break;
			default:
				format = null;
				break;
		}

		if (format == null) {
			return null;
		} else {
			return format.format(date);
		}
	}

	/**
	 * Private constructor, not used as this class has only static methods.
	 */
	private DateTools() {
		// hide constructor
	}
}