package cn.com.taiji.utils;

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

/**
 * @author xhl
 * @date 2022/11/20
 */
public class DateUtils {
    /**
     * 常规日期时间格式，24小时制yyyy-MM-dd HH:mm:ss
     */
    public static final String NORMAL_DATETIME_FORMAT = "yyyy-MM-dd HH:mm:ss";
    /**
     * 常规日期，yyyy-MM-dd
     **/
    public static final String NORMAL_DATE_FORMAT = "yyyy-MM-dd";
    /**
     * 锁对象
     */
    private static final Object LOCK_OBJ = new Object();
    /**
     * 存放不同的日期模板格式的SimpleDateFormat的Map
     */
    private static Map<String, ThreadLocal<SimpleDateFormat>> threadLocalMap = new HashMap<>(8);
    /**
     * 返回一个ThreadLocal的SimpleDateFormat,每个线程只会new一次
     *
     * @param pattern
     * @return
     */
    private static SimpleDateFormat getDateFormat(final String pattern) {
        ThreadLocal<SimpleDateFormat> tl = threadLocalMap.get(pattern);
        // 双重判断和同步,防止threadLocalMap这个单例被多次重复的SimpleDateFormat
        if (tl == null) {
            synchronized (LOCK_OBJ) {
                tl = threadLocalMap.get(pattern);
                if (tl == null) {
                    tl = ThreadLocal.withInitial(() -> new SimpleDateFormat(pattern));
                    threadLocalMap.put(pattern, tl);
                }
            }
        }
        return tl.get();
    }
    /**
     * 日期转字符串
     *
     * @param date
     * @param format
     * @return
     */
    public static String format(Date date, String format) {
        return getDateFormat(format).format(date);
    }
    /**
     * 字符串转日期
     *
     * @param dateStr
     * @param format
     * @return
     * @throws ParseException
     */
    public static Date parse(String dateStr, String format) throws ParseException {
        return getDateFormat(format).parse(dateStr);
    }
}