println is equivalent to using System.out.print(whateverdata + '\n') or System.out.print(whateverdata + "\n"). Java considers \n as a valid linefeed either inline with double quotes similar to C printf, or with single quotes denoting it as a char and not a string. When provided with no data, or data that is empty, it will print only a linefeed.
So:
Code:
System.out.println();
System.out.print('\n');
System.out.print("\n");
Would print three empty lines.