Date size comparison in Java

String beginTime=new String(“2023-01-01 10:10:10”);
String endTime=new String(“2023-02-24 10:10:10”);

1 Directly use Date's own methods before() and after() to compare

SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

  Date sd1=df.parse(beginTime);
  Date sd2=df.parse(endTime);

  System.out.println(sd1.before(sd2));
  System.out.println(sd1.after(sd2));

2 Use String's compareTo() method:

Integer i=beginTime.compareTo(endTime);

System.out.println(i);

Returning a positive value means that the date on the left is greater than the parameter date, and vice versa, the date format must be consistent

3 Convert to date format and change to seconds to compare the number of seconds, getTime() method

 Date sd1=df.parse(beginTime);
  Date sd2=df.parse(endTime);

  long long1 =sd1.getTime()

  long long2= sd2.getTime()

In addition, the mutual conversion method of date and string is attached:

1  Date转String

Date d=new Date();

SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

String ds=df.format(d);

2 String转Date

String ds=new String("2017-06-09 10:22:22"); 

Date sd=df.parse(ds);