判断两个String类型yyyy-MM-dd HH:mm:ss格式的日期大小

可以将字符串转换成Date类型，然后比较两个Date类型的大小。具体实现如下：

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

public class DateCompare {
    public static void main(String[] args) {
        String dateStr1 = "2021-06-01 12:30:00";
        String dateStr2 = "2021-06-01 13:30:00";
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        try {
            Date date1 = format.parse(dateStr1);
            Date date2 = format.parse(dateStr2);
            if (date1.compareTo(date2) < 0) {
                System.out.println(dateStr1 + " is before " + dateStr2);
            } else if (date1.compareTo(date2) > 0) {
                System.out.println(dateStr1 + " is after " + dateStr2);
            } else {
                System.out.println(dateStr1 + " is equal to " + dateStr2);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

输出结果为：

2021-06-01 12:30:00 is before 2021-06-01 13:30:00