im trying to reduce the number of decimals in a double to 8 using println and rounding the last digit up

Question

I've been assigned to output a double:

myD=1.0/3.0; //using println as  0.33333334 = 1/3.

I have tried to use a little bit of formatting with no success.

//0.33333334 = 1/3; //only using println 

double myD = 1.0/3.0
System.out.println("%0.8f", myD);

0.33333334

Its my school assignment. But i guess that's what my teacher wants me to get hehe — Benjamin, Sep 11 '19 at 14:32
I guess that means you're meant to implement the double-to-string algorithm yourself. — Joachim Sauer, Sep 11 '19 at 14:34
I am abit of a newbie, so bear with me. How would one implement a double to string using println? — Benjamin, Sep 11 '19 at 14:35
Presumably using the stuff you recently learned in this course? Unless there's something seriously wrong, you should have been given an assignment that can be solved using the tools you recently learned about. — Joachim Sauer, Sep 11 '19 at 14:37
Yeah i've done similar with .printf. But the other command helped me get on the right track again! thanks alot tho Joachim — Benjamin, Sep 11 '19 at 14:40

score 0 · Accepted Answer · answered Sep 11 '19 at 14:37

Use DecimalFormat and set rounding mode to always round to the CEILING.

double myD = 1.0/3.0;

DecimalFormat df = new DecimalFormat("#.########");
df.setRoundingMode(RoundingMode.CEILING);
System.out.println(df.format(myD));

Output:

0.33333334

If you did not need to round up you could have just used String.format instead to get 0.33333:

System.out.println(String.format("%.8f", myD));

Output:

0.33333333

Of course that could just be System.out.format("%.8f", myD); as well, but the requirements stated to use System.out.println.

im trying to reduce the number of decimals in a double to 8 using println and rounding the last digit up

1 Answers1