SimpleDateFormat问题

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.ZoneOffset;
import java.util.Date;
import java.util.concurrent.TimeUnit;

public class QQ {

    public static void main(String[] args) throws ParseException {

        Long start = System.currentTimeMillis();

        for (int i = 0; i < 100000; i++) {
            SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd 00:05:00");
            SimpleDateFormat dateFormat2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Date date = new Date();
            String dateStr = dateFormat.format(date);
            dateFormat2.parse(dateStr).getTime();

        }

        System.out.println("time1 : " + (System.currentTimeMillis() - start));

        start = System.currentTimeMillis();
        for (int i = 0; i < 100000; i++) {
            Long time = LocalDateTime.of(LocalDate.now(), LocalTime.MIN).toInstant(ZoneOffset.of("+8")).toEpochMilli();
            Long time000 = time + TimeUnit.MINUTES.toMillis(5);
        }
        System.out.println("time2: " + (System.currentTimeMillis() - start));

        System.out
                .println(LocalDateTime.of(LocalDate.now(), LocalTime.MIN).toInstant(ZoneOffset.of("+8")).toEpochMilli()
                        + TimeUnit.MINUTES.toMillis(5));
    }

}

# 链接 

　　》 https://www.cnblogs.com/peida/archive/2013/05/31/3070790.html
# 需要思考的问题：
　　- 线程安全问题

　　- 为什么创建耗时