Re: Removing trailing zeros from java.math.BigDecimal produces infinite loop

From:

"phillip.s.powell@gmail.com" <phillip.s.powell@gmail.com>

Newsgroups:

comp.lang.java.help

Date:

5 Feb 2007 09:31:27 -0800

Message-ID:

<1170696687.671665.125650@l53g2000cwa.googlegroups.com>

On Feb 5, 11:58 am, Eric Sosman <Eric.Sos...@sun.com> wrote:

phillip.s.pow...@gmail.com wrote On 02/05/07 10:16,:

[code]
/**
     * Trim all trailing zeros found after the decimal point of {@link
java.math.BigDecimal}
     * @param n {@link java.math.BigDecimal}
     * @return n {@link java.math.BigDecimal}
     * <a href="http://groups.google.com/group/
comp.lang.java.programmer/browse_frm/thread/5ad5a973fcbf442b/
52012c87f1051dd5?lnk=st&q=removing+trailing+zeros
+java&rnum=2&hl=en#52012c87f1051dd5">more information</a>
     */
    public static BigDecimal trim(BigDecimal n) {
        try {
            while (true) {
                n = n.setScale(n.scale() - 1);
            }
        } catch (ArithmeticException e) {} // DO NOTHING NO MORE
TRAILING ZEROS FOUND
        return n;
    }
[/code]

This method is supposed to remove any and all trailing zeroes from a
given java.math.BigDecimal parameter n and return it "trimmed".

However, if n < 1 or n > -1 the method goes into an infinite loop.
Not sure how to patch this method to prevent this from occurring from
this condition. What tips do you have to prevent this from occurring?
I thought of BigDecimal.ROUND_HALF_UP, but to no avail.

It works fine for me. Can you post a complete program
that demonstrates the problem?

I don't have to, turns out the solution was a lot easier than I could
possibly have imagined (but should have):

n.stripTrailingZeros();

And that's it, a one-liner!

By the way, the idea of using exceptions this way makes
me shudder. The prevailing wisdom is that exceptions should
be, well, "exceptional." For one thing, they're performance
pigs: Creating an Exception object is no lightweight chore.
For another (although it's not much of a concern in the code
you've shown), it's all too easy to catch a "real" exception
in place of the one you were expecting to catch. I think you
would be much better off to begin with something like

BigInteger bi = n.unscaledValue();

... and use BigInteger's methods to discover how many trailing
zeroes there are (you may need a special case for bi == 0) and
adjust the scale of n accordingly.

Thanx, however, the case of removing trailing zeros will occur within
a non-integer value, such as converting "1.20" to "1.2".

--
Eric.Sos...@sun.com