Question

just learning Java and I know this may sound stupid but I have to ask.

System.out.print(new Date());

I know that whatever is in the argument is converted to a string, the end value that is,
new Date() returns a reference to a Date object. So how is it that it prints this?

Mon Aug 29 13:22:03 BST 2011

The only thing I can think of is somehow the function parses through all the data members gets their values converts them to a String and prints them.

If not how does it work?

Thanks

Answer 1

When you print something, the toString() method of that object is called. So it is up to the individual class to provide an implementation that makes sense.

For reference, see

• Java Tutorial: The Object class

And this is Date’s toString() method:

public String toString() {
// "EEE MMM dd HH:mm:ss zzz yyyy";
BaseCalendar.Date date = normalize();
StringBuilder sb = new StringBuilder(28);
int index = date.getDayOfWeek();
if (index == gcal.SUNDAY) {
    index = 8;
}
convertToAbbr(sb, wtb[index]).append(' ');            // EEE
convertToAbbr(sb, wtb[date.getMonth() - 1 + 2 + 7]).append(' ');  // MMM
CalendarUtils.sprintf0d(sb, date.getDayOfMonth(), 2).append(' '); // dd

CalendarUtils.sprintf0d(sb, date.getHours(), 2).append(':');   // HH
CalendarUtils.sprintf0d(sb, date.getMinutes(), 2).append(':'); // mm
CalendarUtils.sprintf0d(sb, date.getSeconds(), 2).append(' '); // ss
TimeZone zi = date.getZone();
if (zi != null) {
    sb.append(zi.getDisplayName(date.isDaylightTime(), zi.SHORT, Locale.US)); // zzz
} else {
    sb.append("GMT");
}
sb.append(' ').append(date.getYear());  // yyyy
return sb.toString();
}