Removing the .0 from a double

问题

I am trying to display numbers in a string dynamically, so if the number has decimal's display them but if not don"t show the .0

example: display 5.5 as 5.5 and 5.0 as 5

This is what I have so far: (answer is a double)

double temp = answer;
long temp2 = (long) temp;
if (temp == temp2) {
output = String.valueOf(temp2);
System.out.println(output);

this work's fine up to about 1e18 then will error out because of the maximum size of a Long. So how would I achieve this on bigger numbers like 5.43e86

回答1:

Use DecimalFormat

double answer = 5.0;
DecimalFormat df = new DecimalFormat("###.#");
System.out.println(df.format(answer));

回答2:

The DecimalFormat suggestions are the easiest way to handle this. If they aren't sufficient, here's another idea.

If you're starting to hit the maximum values that can be represented by primitives in Java, then you may need to move to BigInteger and BigDecimal.

Try playing around with the BigDecimal.toBigInteger() method coupled with the toString() methods on BigDecimal and BigInteger.

回答3:

It's not good solution if you use new DecimalFormat("0.#") you are missing data, for example PI = 3.14, but after parse you ae geting 3.1

Another solution to use eval%1 ? (int)d : d this time couse max integer limit , again missing data

my solution is working, but it's not good idea

res = removeLastChars(eval,".0");

private String removeLastChars(double eval, String text){

    String res = String.valueOf(eval);
    int length = text.length();

    if (res.length() > length){
        res = res.substring((res.length() - length), res.length()).equals(text)
                ? res.substring(0, (res.length() - length)) : res;
    }

    return res;
}

回答4:

Look at http://download.oracle.com/javase/6/docs/api/java/text/DecimalFormat.html

you would want just DecimalFormat("0.0")

来源：https://stackoverflow.com/questions/7109388/removing-the-0-from-a-double

标签

java

double

long-integer