Java: Rounding Numbers (Math.round(), DecimalFormat & printf)

Java enables you to do almost anything, especially tasks involving numbers. But sometimes complicated calculations give you an answer with way too many decimals.
Most practical applications only require a few decimals. Here are 3 ways to round number in Java:

Java's Math class is inherently included in every program you create so there is not need for an import statement. The round() method takes a number as an argument and rounds that number to the nearest integer. On it's own this isn't spectacularly helpful but you can combine it with an easy little trick.

NOTE: The printf method doesn't change the actual contents of the variable. After using printf, the variable still has all the decimals.

3) Using DecimalFormat
Then create a reference variable to a DecimalFormat object: DecimalFormat dFormatter and set it equal to: new DecimalFormat(); In the parentheses, place "0.00" or "#.##" to round to 2 decimals. Add more zeros of ##'s after the period to change the number of decimals.
DecimalFormat formats variables as strings, so if you want to use a number for calculation you have to parse it back to double or float.

[TheDelaneyCurry]

What took me 30 minutes of fumbling through the internet, took you 4 minutes to explain. Thank you!

[phuonghuynh]

Thank you!!! Remember for the formatting, it is important to have "%.2f", number. The comma is very important, do not put +

[christiansgroceryvlogs]

This is the most helpful thing I've ever seen. Quick, concise and I love your voice (it makes it more enjoyable).

[mladboy]

Wow, finally someone explains this in a succinct, but also very clear way! Thank you!

[josealbertofernandez]

BRO I love this. Straight to the point. I watched a 12 min video that left me with more questions than it answered. And yet you did in the first minute 🙏🙏🙏🙏

[Anhjje]

Math.round( value * 1000) / 1000.0 saved my ass for an assignment. Thank you!

[finngrant]

very helpful, thankyou. Ive been coding nearly half a year now and I stupidly forgot how to round to specified decimal places. I was midway through my program and realized I forgot one of the first things I learned

[jacob]

I found the documentation for this function confusing. Now I understand. Thank you!

[sktmx]

life saver for my lab due in an hour and 39 minutes!!

[clea]

best video about these methods, I wish I would've found this much sooner. Thank you!!

[skrublaub]

The rounding part saved me. Thank you!

[christiand]

This video was very helpful. I was looking for so long for this... so simple yet so hard to find. :)

[BennyElie]

You can also simply do casting :


double number = 3.141592653;

double rounded = (int) (number * 100) / 100.0;


System.out.println(rounded);


3.14

[wcsdiaries]

Helped me finish a project in time. Thank you sir!

[sportoman]

Another method I found:
System.out.println(String.format("%.xf", d)); Where x is the # of decimal places you want and d is a double or integer you're working with.

[AmongUs-qtuo]

Thank you so much! I love this trick!

[Bandgeek]

Thank you very much kind sir. I'm a beginner and this helped me out a lot. Thank you!

[minus]

Could you help me out? I need to cut my number without rounding it. And your method rounds the number. For example the number 21.4567 should be shown an 21.45 and not as 21.46, which method could I use? Or what should I do generally?

[rvbCabooservb]

Thanks man, this was the video I was looking for.

[cutieboo]

Thank you hero! Could you please tell me how to make user input to be 2 decimal??