Oracle time formatting

At work, we found that orcale time formatting is a little different from Java time formatting:

For example, in Java, you can write a string in the format of time when the date is changed:

SimpleDateFormat sdf = new SimpleDateFormat ();

Sdf. format ("20:51:03", ''hh: MM: ss ");

The output result is: 20: 51: 03.

Orcale's time is formatted into a character function: to_char

If the style is written in Java format: to_char ('2017-02-27 20:51:03 ', 'hh: mm: ss ');

The output result is 8: 01: 03, which is obviously incorrect.

In this way, the correct result is output: to_char ('2017-02-27 20:51:03 ', 'hh24: mi: ss ');

Output result: 20: 51: 03