Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Android

Posted by Yusuf Mohamed
Yusuf Mohamed
2,631 Points

Question about java/android logic.

I'm currently trying to create a countdown timer for a project of mine. It is working but I was just trying to understand one part.

 private void startStop() {
        if(timerRunning){
            stopTimer();
        } else {
            startTimer();
        }

For some context, timerRunning is a boolean that's set to its default (which is false). The startstop method is a method for used in a onclick method for a button.

So the code says "If false stop timer. Else (if true) start timer".

So if the code by default is false how can it start the timer?

4 Answers

Steve Hunter
Steve Hunter
57,712 Points

Hi Yusuf,

The code will work as you describe.

So if the code by default is false how can it start the timer?

If timerRunning is set to false by default, the else clause will run. The else clause calls the funtion startTimer() which, presumably, makes the time start! 

 private void startStop() {
        if(timerRunning){
            stopTimer(); // this won't run if timerRunning is false
        } else {
            startTimer(); // but this will run so your timer will start
        }
} // I added this

I hope that helps.

Steve.

Yusuf Mohamed
Yusuf Mohamed
2,631 Points

Okay so when the value is false, that's when the else clause will run.

KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,968 Points
KRIS NIKOLAISEN
KRIS NIKOLAISEN
54,968 Points

Wouldn't the logic be if timer is running (timerRunning = true) stop timer? How do you stop the timer if it isn't running? It is already stopped.

Yusuf Mohamed
Yusuf Mohamed
2,631 Points

That's the problem I'm not understanding, it shouldn't work the way I'm doing it but the timer is working so idk if there's something we're missing.

Yusuf Mohamed
Yusuf Mohamed
2,631 Points
Yusuf Mohamed
Yusuf Mohamed
2,631 Points

Bumpidity bump.

Lauren Moineau
Lauren Moineau
9,483 Points
Lauren Moineau
Lauren Moineau
9,483 Points

Hi Yusuf. Actually, your code reads "if true, stop timer, else, start timer", so it works perfectly.

Writing 

 if (timerRunning){
 // (..)
 }

is the same as writing

 if (timerRunning == true) {
 // (...)
 }

I know it's confusing at first.

By the way, if you'd like to check if a Boolean has a value of false, just write

 if (! timerRunning) {. // Instead of (timerRunning == false)
 // (...)
 }

Hope that helps :)