Why doesn't BigDecimal.stripTrailingZeros() remove always all trailing zeros?

Question

I do the following

    MathContext context = new MathContext(7, RoundingMode.HALF_UP);
    BigDecimal roundedValue = new BigDecimal(value, context);

    // Limit decimal places
    try {
        roundedValue = roundedValue.setScale(decimalPlaces, RoundingMode.HALF_UP);
    } catch (NegativeArraySizeException e) {
        throw new IllegalArgumentException("Invalid count of decimal places.");
    }
    roundedValue = roundedValue.stripTrailingZeros();

    String returnValue = roundedValue.toPlainString();

In case the input is now "-0.000987654321" (= value) I get back "-0.001" (= return Value) which is ok.

In case the input is now "-0.0000987654321" I get back "-0.0001" which is also ok.

But when the input is now "-0.00000987654321" I get back "0.0000" instead of "0" which is not ok. What is wrong here? Why aren't the trailing zeros removed in this case?

Answer 1

BigDecimal d = new BigDecimal("0.0000");
System.out.println(d.stripTrailingZeros());

prints 0.0000 with Java 7 but 0 with Java 8. This is apparently a bug that has been fixed in Java 8.

Answer 2

From the description of BigDecimal's stripTrailingZeros:

"Returns a BigDecimal which is numerically equal to this one but with any trailing zeros removed from the representation. For example, stripping the trailing zeros from the BigDecimal value 600.0, which has [BigInteger, scale] components equals to [6000, 1], yields 6E2 with [BigInteger, scale] components equals to [6, -2]"

In other words, it doesn't do what you want it to do. Instead, use the setScale(0) method. The following piece of testcode I wrote give the following output:

    BigDecimal d = new BigDecimal("0.0000");
    System.out.println(d.toString());
    d = d.setScale(0);
    System.out.println(d.toString());

0.0000
0

EDIT: When doing this for 0.0001, you get an error. You need to set the roundingmode as well. (Overload for setScale) You'll have to figure out something to work around that.