format() from SimpleDateFormat class helps to convert a Date object into certain format String object by using the supplied pattern string.

Date today = new Date();
    
SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MMM-yy"); //pattern is specified here
System.out.println(dateFormat.format(today)); //25-Feb-16

Patterns can be applied again by using applyPattern()

dateFormat.applyPattern("dd-MM-yyyy");
System.out.println(dateFormat.format(today)); //25-02-2016

dateFormat.applyPattern("dd-MM-yyyy HH:mm:ss E");
System.out.println(dateFormat.format(today)); //25-02-2016 06:14:33 Thu

Note: Here mm (small letter m) denotes minutes and MM (capital M) denotes month. Pay careful attention when formatting years: capital “Y” (Y) indicates the “week in the year” while lower-case “y” (y) indicates the year.