How can you suppress the automatic suffixing of ".0" for integral cases when stringifying a Double?

Question

Consider

Double f = 2.0;
String s = f.toString();

The resulting string s is "2.0". How can I format f so the answer for the case where f doesn't have a decimal part doesn't have the .0 appended? (For cases where f has a decimal part, I need that to be included.). Yes, for some reason, the toString() method on a Double appends .0 for the case where the Double is an integer.

A nasty hack would be

f % 1.0 == 0.0 ? new Integer(f.intValue()).toString() : f.toString();

but to me that looks terrible.

Btw, `new Integer(f.intValue()).toString()` -> `String.valueOf( f.intValue() )` or `"" + f.intValue()`. — Thomas, Apr 20 '17 at 14:43
@Thomas: The ternary doesn't look so bad if you write it like that. — Xavier Imbs, Apr 20 '17 at 14:45
Possible duplicate of [String.format() to format double in java](http://stackoverflow.com/questions/4885254/string-format-to-format-double-in-java) — Michael, Apr 20 '17 at 14:45
Not really. That dupe is about inserting decimal and thousands separator. Mine is about suppressing an unnecessary .0 — Xavier Imbs, Apr 20 '17 at 14:47

Yahya · Accepted Answer · 2017-04-20T15:16:06.700

2

if I understand your question properly, you may try this:

    double f = 2.0;
    int i = (int)f;
    if (i==f){
        String s = String.valueOf(new DecimalFormat("#").format(f));
        System.out.println(s);
    }
    else{
        String s = String.valueOf(new DecimalFormat("#.###").format(f)); // for example
        System.out.println(s);
    }
}

//now if the number after the point is fully zero, it will not take it

results

f=2.0 -> s=2
f=2.005 -> s=2.005

EDIT: in a few lines if there is no specific "number of digits" after decimal -> you can use the ternary operator like this

double f = 2.000;
int i = (int)f;
String s = (f==i)? String.valueOf(i): String.valueOf(f);
System.out.println(s);

edited Apr 20 '17 at 15:16

answered Apr 20 '17 at 14:55

Yahya

13,349
6
30
42

1

Yes dealing with the integer case separately does seem to be the only way. – Xavier Imbs Apr 20 '17 at 14:58
1

Now this is wonderful. I much prefer the symmetry in the ternary to the way I have it. I don't really like using `toString()`. Many thanks. – Xavier Imbs Apr 20 '17 at 15:16
I'm glad I was able to help – Yahya Apr 20 '17 at 15:16

ΦXocę 웃 Пepeúpa ツ · Answer 2 · 2017-04-20T15:04:17.843

0

You can use a several help methods of several classes to achieve the same result:

    Double f = 2.0;
    String s = null;
    // option1: https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#valueOf-int-
    s = String.valueOf(f.intValue());
    System.out.println(s);
    // option2: https://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html#toString-int-
    s = Integer.toString(f.intValue());
    System.out.println(s);
    // option3: https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#format-java.lang.String-java.lang.Object...-
    s = String.format("%.0f", f);
    System.out.println(s);
    // option4: https://docs.oracle.com/javase/8/docs/api/java/text/DecimalFormat.html#DecimalFormat-java.lang.String-
    s = new DecimalFormat("#").format(f);
    System.out.println(s);

for an input like:

Double f = 21231.232222323;

the output will be: 21231

edited Apr 20 '17 at 15:04

answered Apr 20 '17 at 14:43

ΦXocę 웃 Пepeúpa ツ

47,427
17
69
97

But these seem to truncate a decimal like 2.1 or 123.456 – Xavier Imbs Apr 20 '17 at 14:59
which option do you mean? – ΦXocę 웃 Пepeúpa ツ Apr 20 '17 at 15:01
Well `f.intVal` is certainly going to remove the decimal component. My understanding is that "%.0f" will do the same, and so on. – Xavier Imbs Apr 20 '17 at 15:01

gusto2 · Answer 3 · 2017-04-20T14:50:41.900

0

Using the number format (for more advanced formatting)

NumberFormat nf = NumberFormat.getInstance();
nf.setMaximumFractionDigits(2);
System.out.println(nf.format(f));

edited Apr 20 '17 at 14:50

answered Apr 20 '17 at 14:47

gusto2

11,210
2
17
36

Will this preserve the decimal parts of things like 2.1 and 666.6? – Xavier Imbs Apr 20 '17 at 14:49
you are right, I fixed the answer. The NumberFormat should not print unnecessary decimals when not needed – gusto2 Apr 20 '17 at 14:51
Won't this truncate 123.456 to 123.45? – Xavier Imbs Apr 20 '17 at 14:52
it will, you may skip setting the maximum fraction digits. It is there to demonstrate the options for formatting – gusto2 Apr 20 '17 at 14:53

Xavier Imbs · Answer 4 · 2017-04-20T15:01:04.757

0

It seems there is no trivial formatter that does this. Using (thanks to @Thomas for the simplification of the integer case)

f % 1.0 == 0.0 ? String.valueOf(f.intValue()) : f.toString();

seems to be the best way.

f % 1.0 is a good way to test for integral f in Java.

edited Apr 20 '17 at 15:01

answered Apr 20 '17 at 14:53

Xavier Imbs

212
2
10

score 0 · Answer 5 · answered Apr 20 '17 at 15:10

0

As suggested in the comments, try DecimalFormat.

static void show(double v){
    DecimalFormat format = new DecimalFormat("##########.##");
    System.out.println(format.format(v));
}
public static void main (String[] args) throws java.lang.Exception
{
    show(1.1);
    show(1.0);
    show(1.15);
    show(1.116);
}

The out put will be:

1.1

1

1.15

1.12

Which seems like what you're looking for.

answered Apr 20 '17 at 15:10

matt

10,892
3
22
34

No. 1.116 needs to be 1.116. – Xavier Imbs Apr 20 '17 at 15:11
Do you have a maximum number of places? Just add more `#`s. – matt Apr 20 '17 at 15:12

How can you suppress the automatic suffixing of ".0" for integral cases when stringifying a Double?

5 Answers5