import java.util.Objects;

public class CommonUtilsTest {
    public static void main(String[] args) {
        testObjectsEquals();
    }

    public static void testObjectsEquals() {
        String a = null;
        String b = null;
        System.out.println(Objects.equals(a, b)); // true

        String c = "1";
        String d = "1";
        System.out.println(Objects.equals(c, d)); // true

        String[] aa = new String[] {"1", "2"};
        String[] bb = new String[] {"1", "2"};
        System.out.println(Objects.equals(aa, bb)); // false

        String[] cc = new String[] {"1", "2"};
        String[] dd = new String[] {"1", "2"};
        System.out.println(Objects.deepEquals(cc, dd)); // true		
    }
}

import java.util.Calendar;
import java.util.Date;

public class DateUtils {
    /**
     * yyyy
     */
    public static final String yyyy = "yyyy";

    /**
     * yyyy-MM
     */
    public static final String yyyy_MM = "yyyy-MM";

    /**
     * yyyy-MM-dd
     */
    public static final String yyyy_MM_dd = "yyyy-MM-dd";

    /**
     * yyyyMMddHHmmss
     */
    public static final String yyyyMMddHHmmss = "yyyyMMddHHmmss";

    /**
     * yyyy-MM-dd HH:mm:ss
     */
    public static final String yyyy_MM_dd_HH_mm_ss = "yyyy-MM-dd HH:mm:ss";

    /**
     * yyyy-MM-dd HH:mm:ss.SSS
     */
    public static final String yyyy_MM_dd_HH_mm_ss_SSS = "yyyy-MM-dd HH:mm:ss.SSS";
    
    /**
     * 格式化给定日期时间部分00:00:00.000
     * 
     * @param date
     * @return
     */
    public static Date formatDateBegin(Date date) {
        Calendar calendar = Calendar.getInstance();

        calendar.setTime(date);

        // 时
        calendar.set(Calendar.HOUR_OF_DAY, 0);
        // 分
        calendar.set(Calendar.MINUTE, 0);
        // 秒
        calendar.set(Calendar.SECOND, 0);
        // 毫秒
        calendar.set(Calendar.MILLISECOND, 0);

        return calendar.getTime();
    }

    /**
     * 格式化时间(格式化给定日期时间部分为23.59.59.999)
     * 
     * @param date
     * @return
     */
    public static Date formatDateEnd(Date date) {
        Calendar calendar = Calendar.getInstance();

        calendar.setTime(date);

        // 时
        calendar.set(Calendar.HOUR_OF_DAY, 23);
        // 分
        calendar.set(Calendar.MINUTE, 59);
        // 秒
        calendar.set(Calendar.SECOND, 59);
        // 毫秒
        calendar.set(Calendar.MILLISECOND, 999);

        return calendar.getTime();
    }
    
    /**
     * 将10 或 13 位时间戳转换为时间格式字符串
     * @param str
     * @param format
     * @return
     */
    public static String parseTimestampToDateStr(String str, String format) {
        SimpleDateFormat sdf = new SimpleDateFormat(format);
        if (str.length() == 13) {
            String date = sdf.format(new Date(Long.parseLong(str)));
            return date;
        } else {
            String date = sdf.format(new Date(Integer.parseInt(str) * 1000L));
            return date;
        }
    }
    // System.out.println(timestamp2Date("1610710393219", "yyyy-MM-dd HH:mm:ss")); // 2021-01-15 19:33:13
    // System.out.println(timestamp2Date("1614758431", "yyyy-MM-dd HH:mm:ss"));    // 2021-03-03 16:00:31
}