easyexcel/src/main/java/com/alibaba/excel/util/DateUtils.java

package com.alibaba.excel.util;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

import com.alibaba.excel.exception.ExcelDataConvertException;

/**
 * Date utils
 *
 * @author zhuangjiaju
 **/
public class DateUtils {
    public static final String DATE_FORMAT_14 = "yyyyMMddHHmmss";
    public static final String DATE_FORMAT_17 = "yyyyMMdd HH:mm:ss";
    public static final String DATE_FORMAT_19 = "yyyy-MM-dd HH:mm:ss";
    public static final String DATE_FORMAT_19_FORWARD_SLASH = "yyyy/MM/dd HH:mm:ss";
    private static final String MINUS = "-";

    private DateUtils() {}

    /**
     * convert string to date
     * 
     * @param dateString
     * @param dateFormat
     * @return
     * @throws ParseException
     */
    public static Date parseDate(String dateString, String dateFormat) throws ParseException {
        if (StringUtils.isEmpty(dateFormat)) {
            dateFormat = switchDateFormat(dateString);
        }
        return new SimpleDateFormat(dateFormat).parse(dateString);
    }

    /**
     * convert string to date
     *
     * @param dateString
     * @return
     * @throws ParseException
     */
    public static Date parseDate(String dateString) throws ParseException {
        return parseDate(switchDateFormat(dateString), null);
    }

    /**
     * switch date format
     *
     * @param dateString
     * @return
     */
    private static String switchDateFormat(String dateString) {
        int length = dateString.length();
        switch (length) {
            case 19:
                if (dateString.contains(MINUS)) {
                    return DATE_FORMAT_19;
                } else {
                    return DATE_FORMAT_19_FORWARD_SLASH;
                }
            case 17:
                return DATE_FORMAT_17;
            case 14:
                return DATE_FORMAT_14;
            default:
                throw new ExcelDataConvertException("can not find date format for：" + dateString);
        }
    }

    /**
     * Format date
     * <p>
     * yyyy-MM-dd HH:mm:ss
     * 
     * @param date
     * @return
     */
    public static String format(Date date) {
        return format(date, null);
    }

    /**
     * Format date
     * 
     * @param date
     * @param dateFormat
     * @return
     */
    public static String format(Date date, String dateFormat) {
        if (date == null) {
            return "";
        }
        if (StringUtils.isEmpty(dateFormat)) {
            dateFormat = DATE_FORMAT_19;
        }
        return new SimpleDateFormat(dateFormat).format(date);
    }
}