Remove trailing zeroes after decimal from double

Question

I am writing a program to get the average of two numbers. For test case, 2, 4 the output should be 3 not 3.0. For test case, -1282660896, -672813783 the output should be -977737339.5 not -9.777373395E8.

My code is like this:

public static void getAve(long a, long b){
     System.out.println((double)(a + b) / 2);
}

I also created a format function to meet my need, like this:

public static String fmt(double d) {
        if (d == (long) d)
            return String.format("%d", (long) d);
        else
            return String.format("%s", d);
    }

But this also fails for test case 2

You need a format which doesn't switch to scientific notation. I suggest you look at the others, or use `new DecimalFormat("0.#").format(d)` — Peter Lawrey, Oct 27 '13 at 19:53
You can keep the DecimalFormat object as a constant to improve performance. — Peter Lawrey, Oct 27 '13 at 20:13

score 0 · Accepted Answer · edited May 23 '17 at 11:57

0

For your case, you can do String.format("%d", (int)d) but only in the case if d doesn't have a decimal part.

Actually there is already an answer for that:

How to nicely format floating numbers to String without unnecessary decimal 0?

edited May 23 '17 at 11:57

Community

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answered Oct 27 '13 at 19:54

Ashalynd

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If you're going to cast a double to `int`, you'll lose the data after the comma altogether. – Jeroen Vannevel Oct 27 '13 at 19:55
true, you can only do it in that special case when there is no decimal part. – Ashalynd Oct 27 '13 at 19:57

score 0 · Answer 2 · answered Oct 27 '13 at 20:01

For the case 2, you want to use a format that doesn't use scientific notation and specify the precision:

return String.format("%.1f", d);  // only one digit fractional precision

See http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#syntax

Also, comparing double to int is dangerous, since double is not guaranteed to represent exactly an integer. You'd better check if it close to an integer up to a predefined epsilon.

Remove trailing zeroes after decimal from double

2 Answers2