Java: Referring to the object before the dot operator in a method

Question

So, here is the issue. I made a Time class which allows me to create time objects. In my time class, I created a method called minutesUntil. minutesUntil tells me the difference in minutes between two times.

To call minutesUntil, I used this line.

time1.minutesUntil(time2)

This is the code in minutesUntil.

 public int minutesUntil(Time other){
    int otherTotalMinutes = other.getMinutes() + (other.getHours() * 60);
    int thisTotalMinutes = ??.getMinutes() + (??.getHours() * 60);
    return (otherTotalMinutes - thisTotalMinutes);
}

What do I use in place of the question marks on the third line to refer to the time1 object inside of the minutesUntil method.

Inside instance methods (and constructors), you have a reference to the current instance in the form of the keyword `this`. — Sotirios Delimanolis, Apr 29 '14 at 01:21
possible duplicate of [When should I use "this" in a class?](http://stackoverflow.com/questions/2411270/when-should-i-use-this-in-a-class) — Joshua Taylor, Apr 29 '14 at 01:38

score 3 · Answer 1 · answered Apr 29 '14 at 01:22

3

If I understand you correctly, you want this; that is

int thisTotalMinutes = ??.getMinutes() + (??.getHours() * 60);

should be

int thisTotalMinutes = this.getMinutes() + (this.getHours() * 60);

Which might also be expressed like

// Using "this" implicitly.
int thisTotalMinutes = getMinutes() + (getHours() * 60);

answered Apr 29 '14 at 01:22

Elliott Frisch

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Thanks. I thought I was supposed to use 'this.' , but I didn't get the correct value when I ran the program using 'this.', so I assumed my use of 'this.' was incorrect. After trying again, it worked. I assume I made some stupid mistake. Thank You. :) – Underdisc Apr 29 '14 at 01:28
@Underdisc You might need to check which one has a greater value before performing the subtraction. – Elliott Frisch Apr 29 '14 at 01:29
That was the first thing I checked and it is working exactly as intended now. Thanks again. :) – Underdisc Apr 29 '14 at 01:31

score 2 · Answer 2 · answered Apr 29 '14 at 01:23

You don't need anything there. Get rid of the dots. Change this:

int thisTotalMinutes = ??.getMinutes() + (??.getHours() * 60);

to this:

int thisTotalMinutes = getMinutes() + (getHours() * 60);

Or use this if you desire, but I see no need to clutter the code with this in this situation.

Java: Referring to the object before the dot operator in a method

2 Answers2