Print double with exact length in java

Question

I could not find answer for my question on the net, so that's why I'm here.

I want to print a number with specified number of digits example in java:

Length = 10

1.123456789      ==> 1.123456789

123.123456789    ==> 123.1234567

123456.123456789 ==> 123456.1234

I'm trying different format methods, but nothing works so far, and yes i need a number with exact number of digits . — Християн Христов, Nov 18 '16 at 10:36

Konstantin Yovkov · Answer 1 · 2016-11-18T10:39:19.680

2

It seems you need to fetch the first n digits from the String representation of the number. However, the decimal separator should not be counted as a digit:

String printNumber(double number, int n) {
   String value = String.valueOf(number);
   String result = "";
   int count = 0;
   for (char c : value.toCharArray()) {
       if (count == n) break;
       if (c != '.') {
           count++;
       }
       result += c;
   }
   return result;
}

edited Nov 18 '16 at 10:39

answered Nov 18 '16 at 10:33

Konstantin Yovkov

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only need to check if there is a decimal part here, the separator is not count ;) – AxelH Nov 18 '16 at 10:34
100.1 wont work for n==4 – xro7 Nov 18 '16 at 10:35
@xro7, true. Will update the answer. – Konstantin Yovkov Nov 18 '16 at 10:36

Nurjan · Answer 2 · 2016-11-18T10:42:23.787

1

You can try this:

Double number = 1.123456789;
BigDecimal bigDecimal = new BigDecimal(number).setScale(6, RoundingMode.HALF_EVEN);
System.out.println("double value: " + bigDecimal.doubleValue());

In the setScale method you can choose number of digits after dot.

edited Nov 18 '16 at 10:42

answered Nov 18 '16 at 10:31

Nurjan

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score 0 · Answer 3 · answered Nov 18 '16 at 10:31

Well, you can calculate the amount based on the length of the non-decimal number:

public String doubleToString(double in) {
    int length = (((int) in) + "").length(); //non-decimal length
    if (length <= 0 || length > 10) {
        //error out? not sure how you wish to handle 11-digit numbers
    }
    return String.format("%." + (10 - length) + "f", in); //format decimal
}

Shortened:

//default to 0 decimals for >10 digits
public String doubleToString(double in) {
    return String.format("%." + Math.max(0, (10 - (((int) in) + "").length()) + "f", in);
}

score 0 · Accepted Answer · answered Nov 18 '16 at 10:31

0

save the number as string and take the substring from 0 to 10. now you can parse it back and got the number with 10 digits

answered Nov 18 '16 at 10:31

Aelop

156
9

Print double with exact length in java

4 Answers4