Java使用DecimalFormat进行奇怪的舍入

Question

double number = Scanner.nextDouble();    
DecimalFormat df = new DecimalFormat("#.#");
        System.out.print (df.format(number));

I've tried the above for rounding my number to 1 decimal place but in cases where there are no decimal numbers, it seems to round to an integer value (for example 2.0 would be displayed as 2). I want 2.0, as well as any other input number to display in 1 decimal place. Also, when DecimalFormat rounds a negative number to 0, it turns it to -0. How can I solve these issues?

Answer 1

Use "0.0" as your format string. # means a digit, or blank if zero which is what you're seeing.

For getting rid of the sign, take a look at this answer .

Answer 2

There is nothing strange about the output. The format is just not as per your requirement.

In DecimalFormat # will only output the character in its specified decimal place if it makes sense. So 10.00 will simply be 10. If you want decimal places to be significant you need to use 0 .

new DecimalFormat("#.0");

Sample output for this would be:

0.11 - .1
10.00 - 10.0
10.4545 - 10.5
.00 - .0
455 - 455.0

If you want a 0 before decimal too, then you can user #0.0